Method for manufacturing prepreg, coating device, and apparatus for manufacturing prepreg

ABSTRACT

The present invention relates to a method of producing a prepreg, in which a matrix resin is applied to a reinforcing fiber sheet, where the sheet can continuously run without clogging due to generated fuzz, even at a high running speed, and where the sheet can be efficiently impregnated with the matrix resin. The prepreg is produced by a method which includes a step of allowing a reinforcing fiber sheet to pass horizontally or slantingly through the inside of a coating section storing a matrix resin to apply the matrix resin to the reinforcing fiber sheet, where the coating section includes a liquid pool and a narrowed section which are in communication with each other, where the liquid pool has a portion whose cross-sectional area decreases continuously along a running direction of the reinforcing fiber sheet, and wherein the narrowed section has a slit-like cross-section and has a smaller cross-sectional area than the largest cross-sectional area of the liquid pool.

CROSS REFERENCE TO RELATED APPLICATIONS

This is the U.S. National Phase application of PCT/JP2019/029607, filedJul. 29, 2019 which claims priority to Japanese Patent Application No.2018-150109, filed Aug. 9, 2018, the disclosures of these applicationsbeing incorporated herein by reference in their entireties for allpurposes.

FIELD OF THE INVENTION

The present invention relates to a method of producing a prepreg, andparticularly relates to a method of producing a prepreg by impregnatinga reinforcing fiber sheet with a matrix resin uniformly.

BACKGROUND OF THE INVENTION

Fiber reinforced composite materials (FRP) in which a matrix resincontaining a thermoplastic resin or a thermosetting resin is reinforcedwith a reinforcing fiber are used in various fields such as aerospacematerials, automobile materials, industrial materials, pressure vessels,construction materials, housings, medical applications, and sportsapplications. Carbon fiber reinforced materials (CFRP) are widely andsuitably used particularly in cases where high mechanical property andlightness are required. On the other hand, in some of the cases wherecost has priority over a mechanical property and lightness, glass fiberreinforced composite materials (GFRP) are used. FRP is obtained byimpregnating a reinforcing fiber bundle with a matrix resin to obtain anintermediate base material, which is laminated and formed, and furtherthermally cured if a thermosetting resin is used, and members composedof FRP are then produced. In the above-mentioned applications, planarobjects or objects formed by folding planar objects are often used, andtwo-dimensional sheet-like objects are more widely used as intermediatebase materials of FRP than one-dimensional strands and roving-likeobjects, from the viewpoint of lamination efficiency and moldabilityachieved in producing such members.

In addition, an attempt to enhance production efficiency for memberscomposed of FRP has recently promoted the mechanization and automationof lamination of sheet-like intermediate base materials, and here,narrow tape-like intermediate base materials are suitably used. Narrowtape-like intermediate base materials can be obtained by slicing broadsheet-like intermediate base materials into tapes having a desired widthor impregnating a narrow reinforcing fiber sheet directly with matrixresins.

A two-dimensional sheet-like intermediate base material that is commonlyused is prepreg. Prepreg is produced by providing and/or impregnating areinforcing fiber with a matrix resin. Examples of reinforcing fibersheets include: a unidirectional material (UD base material) in which aplurality of reinforcing fibers are unidirectionally arranged in planarform; and a reinforcing fiber fabric formed by arranging reinforcingfibers multiaxially or randomly into a sheet.

A hot-melt process that is one of the methods of producing prepregs is amethod in which a matrix resin is melted and then applied onto releasepaper sheets, a laminated structure is produced in which a reinforcingfiber sheet is sandwiched between the matrix resin sheets at the upperside and lower side of the reinforcing fiber sheet, and then, the insideof the reinforcing fiber sheet is impregnated with the matrix resin byheat and pressure. There is a problem in that this method has manysteps, cannot increase the production speed, and is costly.

For more efficient impregnation, for example, Patent Literature 1 hasmade a proposition. This is a method in which glass fiber is melted andspun, and the resulting spinning bundled in strand form or roving formis allowed to pass through a liquid pool filled with a thermoplasticresin and having a conical flow path.

As another example, Patent Literature 2 describes a method in which acoating film is formed on both faces of a sheet-like objectsimultaneously, but this is a method in which a sheet-like object isallowed to pass through a web-guide and coated using a pipe type doctorblade in order to prevent fluctuation of the sheet-like object in theformation of the coating film.

As a method of producing strip-like prepreg using a thermoplastic resin,a horizontal type pultrusion method is known in which a strip-likereinforcing fiber bundle is conveyed in the horizontal direction (crossdirection) and is allowed to pass through a die, where the strip-likereinforcing fiber bundle is provided and impregnated with athermoplastic resin (Patent Literature 3). Patent Literature 3 explainsthat a plurality of strip-like reinforcing fiber bundles are separatelyintroduced into a die filled with molten thermoplastic resin, opened,impregnated, and laminated using a fixed guide (for example, a squeezebar), and finally withdrawn from the die as one sheet of prepreg.

Patent Literature 4 describes a device that causes ultrasonic vibrationat the outlet of a manifold in a pultrusion method in which the manifoldis filled with a thermoplastic resin, from which a reinforcing fiberbundle is pultruded longitudinally.

PATENT LITERATURE

Patent Literature 1: WO2001/028951

Patent Literature 2: JP10-337516A

Patent Literature 3: WO2012/002417

Patent Literature 4: JP01-178412A

SUMMARY OF THE INVENTION

The method in Patent Literature 1 enables only a strand-like orroving-like object to be produced, and is not applicable to producing asheet-like prepreg at which the present invention is directed. Inaddition, Patent Literature 1 explains that, in order to enhanceimpregnation efficiency, a thermoplastic resin fluid is allowed tostrike against a side of the strand-like or roving-like reinforcingfiber bundle to actively generate turbulence in a conical flow path.This is considered to be intended to disturb part of the arrangement ofthe reinforcing fiber bundle so that the matrix resin can flow in, butapplying this idea to a reinforcing fiber sheet conceivably causes thereinforcing fiber sheet to be deformed, resulting in not only degradingthe grade of the prepreg but also decreasing the mechanical property ofFRP.

In addition, if the technology of Patent Literature 2 is applied,abrasion at the web-guide generates fuzz, conceivably making itdifficult for the reinforcing fiber sheet to run. In addition, thetechnology of Patent Literature 2 is intended for coating with resin,not for impregnation.

In addition, the method of Patent Literature 3 makes it more likely thatfuzz is retained in a liquid pool during continuous production and thatthe fuzz clogs a pultrusion portion. There is a problem in that, inparticular, running a strip-like reinforcing fiber bundle continuouslyat a high speed causes the frequency of clogging with fuzz to be veryhigh, and accordingly, enables production to be carried out only at avery low speed and fails to increase productivity.

In a method described in Patent Literature 4, a nozzle portion filledwith no resin is disposed in the portion above a manifold. The nozzlecan be optimized with a strand or a roving-form object but does noteasily cope with a planar shape such as of a reinforcing fiber sheet.While passing through this nozzle, a reinforcing fiber sheet generatesfuzz, which is conceivably more likely to clog a die when brought intothe manifold.

Thus, none of an efficient method of applying a matrix resin to areinforcing fiber sheet and an efficient method of producing a prepreghas been established yet.

An object of the present invention relates to a method of producing aprepreg, and is to provide a production method and a coating device fora prepreg, wherein generation of fuzz is suppressed, continuousproduction is possible without clogging with fuzz, a reinforcing fibersheet is efficiently impregnated with a matrix resin, and the productionspeed can be made higher.

The above-mentioned problem is solved by a method of producing a prepregaccording to the present invention, the method characterized byincluding a step of allowing a reinforcing fiber sheet to passhorizontally or slantingly through the inside of a coating sectionstoring a matrix resin to apply the matrix resin to the reinforcingfiber sheet; wherein the coating section includes a liquid pool and anarrowed section which are in communication with each other, wherein theliquid pool has a portion whose cross-sectional area decreasescontinuously along a running direction of the reinforcing fiber sheet,and wherein the narrowed section has a slit-like cross-section and has asmaller cross-sectional area than the largest cross-sectional area ofthe liquid pool; and wherein the width L at the ends of the liquid pooland the width W of the sheet-like reinforcing fiber bundle at the outletof the narrowed section satisfy the relationship of the below-mentionedFormula (1).

L≤W+10 (mm)  (1)

In addition, a coating device according to the present invention is acoating device for applying a matrix resin to a reinforcing fiber sheet,the coating device characterized by including: a running mechanism whichallows the reinforcing fiber sheet to run horizontally or slantingly,and a coating mechanism; wherein said coating mechanism is capable ofstoring a matrix resin in the inside thereof, and further includes aliquid pool and a narrowed section which are in communication with eachother, wherein said liquid pool has a portion whose cross-sectional areadecreases continuously along a running direction of said reinforcingfiber sheet, and wherein said narrowed section has a slit-likecross-section and has a smaller cross-sectional area than the largestcross-sectional area of the liquid pool.

Furthermore, a prepreg production apparatus according to the presentinvention is characterized by including: a rack on which a reinforcingfiber or a reinforcing fiber fabric is hung; the above-mentioned coatingdevice; and a winder for winding up a prepreg.

The method of producing a prepreg according to the present inventionmakes it possible to significantly suppress and prevent clogging withfuzz. Furthermore, the method enables the reinforcing fiber sheet to berun continuously at a high speed, and enhances the productivity of theprepreg.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic cross-sectional view depicting a production methodand coating device for a prepreg according to one embodiment of thepresent invention.

FIG. 2 is a schematic cross-sectional view depicting a production methodand coating device for a prepreg according to another embodiment of thepresent invention.

FIG. 3 is a schematic cross-sectional view depicting a production methodand coating device for a prepreg according to another embodiment of thepresent invention.

FIG. 4 is a schematic cross-sectional view depicting a production methodand coating device for a prepreg according to another embodiment of thepresent invention.

FIG. 5 is a cross-sectional view depicting the structure of the outletof the coating section 20 in FIG. 1, as viewed in the direction oppositeto X in FIG. 1.

FIG. 6 is a cross-sectional view depicting the structure of the insideof the coating section 20 in FIG. 1, as viewed in the direction Z inFIG. 1.

FIG. 7 is a cross-sectional view depicting the circular stream of thematrix resin 2 in the clearance gap 33 in FIG. 6.

FIG. 8 is a view depicting an installation example of a width regulationmechanism.

FIG. 9 is a detailed cross-sectional view of the outlet region of thecoating section 20 according to the embodiment in FIG. 1.

FIG. 10 is a detailed cross-sectional view of the outlet region of thecoating section 20 b according to an embodiment other than in FIG. 9.

FIG. 11 is a detailed cross-sectional view of the outlet region of thecoating section 20 c according to an embodiment other than in FIG. 9.

FIG. 12 is a detailed cross-sectional view of the outlet region of thecoating section 20 d according to an embodiment other than in FIG. 9.

FIG. 13 is a detailed cross-sectional view of the outlet region of thecoating section 40 according to an embodiment other than of the presentinvention.

FIG. 14 is a detailed cross-sectional view of the coating section 20 eaccording to an embodiment other than in FIG. 9.

FIG. 15 is a schematic diagram depicting an example of aprocess/apparatus for producing a prepreg using the present invention.

FIG. 16 is a schematic diagram of an example of anotherprocess/apparatus for producing a prepreg using the present invention.

FIG. 17 is a schematic diagram of an example of anotherprocess/apparatus for producing a prepreg using the present invention.

FIG. 18 is a diagram depicting an example of an aspect in which aplurality of coating sections are included, wherein the aspect isaccording to one embodiment of the present invention.

FIG. 19 is a diagram depicting an example of an aspect in which aplurality of prepregs are laminated, wherein the aspect is according toone embodiment of the present invention.

FIG. 20 is a diagram showing the simulation result (liquid pressure)obtained with H=50.

FIG. 21 is a diagram showing the simulation result (liquid flow)obtained with H=50.

FIG. 22 is a diagram showing the simulation result (liquid pressure)obtained with H=1.

FIG. 23 is a diagram showing the simulation result (liquid flow)obtained with H=50.

FIG. 24 is a diagram showing the simulation result (liquid pressure)obtained with H=0.

FIG. 25 is a diagram showing the simulation result (liquid flow)obtained with H=0.

FIG. 26 is a diagram showing the simulation results (liquid flow andflow velocity) obtained with H changed.

FIG. 27 is a detailed cross-sectional view of the coating section 20 faccording to an embodiment other than in FIG. 9.

FIG. 28 is a schematic diagram of an example of anotherprocess/apparatus for producing a prepreg using the present invention.

FIG. 29 is a detailed cross-sectional view of the coating section 20 gaccording to an embodiment other than in FIG. 9.

FIG. 30 is a schematic diagram of an example of anotherprocess/apparatus for producing a prepreg using the present invention.

FIG. 31 is a schematic diagram of an example of anotherprocess/apparatus for producing a prepreg using the present invention.

FIG. 32 is a detailed cross-sectional view of the coating section 20 haccording to an embodiment other than in FIG. 9.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

Preferred embodiments of the present invention will be described withreference to the drawings. In this regard, the following descriptionillustrates embodiments of the present invention, the present inventionis not to be construed to be limited to the embodiments, and variousmodifications can be made to the invention to the extent that they donot depart from the object and effect of the present invention.

<Outline of Method of Producing Prepreg>

First, the outline of the method of producing a prepreg according to thepresent invention will be described with reference to FIG. 1. FIG. 1 isa schematic cross-sectional view depicting a method and apparatus forproducing a prepreg according to one embodiment of the presentinvention. A coating device 100 includes: conveyance rolls 14 and 15 asa running mechanism for running a reinforcing fiber sheet 1 bhorizontally or slantingly; and a coating section 20 that is disposedbetween the conveyance rolls 14 and 15 and stores a matrix resin 2. Thematrix resin may itself be fluid, or may contain a solvent, aplasticizer, or the like to obtain fluidity. Also before and after thecoating device 100, it is possible to provide a plurality of creels 11for unwinding reinforcing fibers 1 a, an arrangement device 13 forobtaining a reinforcing fiber sheet 1 b in which the unwound reinforcingfibers 1 a are arranged unidirectionally (arranged in the depthdirection of the page in FIG. 1), and a wind-up device 17 for a prepreg1 d, and in addition, the coating device 100 is equipped with amonitoring means for the amount of the matrix resin and a supply devicefor the matrix resin, though neither the monitoring means nor the supplydevice is shown in the drawing (as in the other examples). Furthermore,the coating device 100 includes a supply device 16 a for supplying arelease sheet 3 and a supply device 16 b for supplying a resin film 4.

<Reinforcing Fiber Sheet>

Here, examples of reinforcing fibers include carbon fibers, glassfibers, metal fibers, metal oxide fibers, metal nitride fibers, organicfibers (aramide fibers, polybenzoxazole fibers, polyvinyl alcoholfibers, polyethylene fibers, polyester fibers, polyamide fibers, and thelike), and the like, and carbon fibers are preferably used, from theviewpoint of the mechanical property and lightness of FRP.

Examples of reinforcing fiber sheets include: a unidirectional material(UD base material) in which a plurality of reinforcing fibers areunidirectionally arranged in planar form; and a reinforcing fiber fabricformed by arranging reinforcing fibers multiaxially or randomly into asheet.

The UD base material is not limited to any particular forming method,and may be formed using a known method. It is preferable from theviewpoints of process efficiency and arrangement uniformity topreliminarily arrange single fibers to form a reinforcing fiber bundle,followed by further arranging the reinforcing fiber bundle to form areinforcing fiber sheet. For example, in the case of carbon fiber, a“tow” that is a tape-like reinforcing fiber bundle is wound on a bobbin,and a reinforcing fiber sheet can be obtained by arranging the tape-likereinforcing fiber bundle withdrawn from the bobbin. In addition, it ispreferable to have a reinforcing fiber arrangement mechanism for orderlyarranging reinforcing fiber bundles withdrawn from the bobbins fit ontothe creels so that there can be no undesirable overlapping nor foldingin the reinforcing fiber bundles in the reinforcing fiber sheet and nosplit between the reinforcing fiber bundles. As a reinforcing fiberarrangement mechanism, a known roller, a comb type of arrangementdevice, or the like can be used. In addition, layering a plurality ofpreliminarily arranged reinforcing fiber sheets is useful from theviewpoint of decreasing gaps between the reinforcing fibers. In thisregard, the creels are preferably provided with a tension controlmechanism operated when the reinforcing fibers are withdrawn. As atension control mechanism, a known one can be used, and examples thereofinclude a braking mechanism. In addition, tension can also becontrolled, for example, by adjusting a yarn guide.

On the other hand, specific examples of reinforcing fiber fabricsinclude not only woven fabrics, knitted fabrics, and the like but alsotwo-dimensionally and multiaxially arranged reinforcing fibers andrandomly oriented reinforcing fibers such as non-woven fabrics, mats,and paper. In this case, the reinforcing fiber can be formed into asheet by utilizing a method such as binder-providing, confounding,welding, or fusing. Examples of woven fabrics that can be used includenot only basic fabric structures such as plain weaves, twill, satin, andnon-crimp fabrics but also bias structures, leno weaves, multiaxiallywoven fabrics, multi-woven fabrics, and the like. In a woven fabricformed by combining a bias structure and a UD base material, not onlythe UD structure inhibits the woven fabric from being deformed by atension in a matrix resin application (referred to as coating in somecases) process and an impregnating process, but also the bias structurealso causes quasi-isotropy, and thus, is a preferable form. In addition,a multi-woven fabric is advantageous in that the upper face and/or lowerface of the woven fabric and the structure and properties of the insideof the woven fabric can be designed separately. A preferable knittedfabric is warp knitting taking into consideration the shape stability inthe coating/impregnating process, and it is also possible to use braidwhich is circular knitting.

Among these, a UD base material is preferably used in cases where themechanical property of FRP is prioritized, and a UD base material can beproduced by a known method of arranging reinforcing fibersunidirectionally in sheet form.

<Smoothing of Reinforcing Fiber Sheet>

In the present invention, increasing the surface smoothness of thereinforcing fiber sheet can enhance the uniformity of the amount of thematrix resin applied in the coating section. For this reason, thereinforcing fiber sheet is preferably introduced into the liquid poolafter it is smoothed. The smoothing treatment method is not limited to aparticular one, and examples thereof include a method in which physicalpressure is applied using opposing rolls or the like and a method inwhich reinforcing fibers are moved using air flow. A method in whichphysical pressure is applied is easy and convenient, less likely todisturb the arrangement of the reinforcing fibers, and accordinglypreferable. More specifically, calendering or the like can be used. Themethod in which air flow is used not only is less likely to causeabrasion but also has the effect of widening a reinforcing fiber sheet,and accordingly, is preferable.

<Widening of Reinforcing Fiber Sheet>

In the present invention, it is also preferable from the viewpoint ofenabling a thin prepreg to be produced efficiently that the reinforcingfiber sheet is introduced into the liquid pool after it is treated forwidening of the fiber bundle. The treatment method of widening of thefiber bundle is not limited to a particular one, and examples thereofinclude a method in which vibration is applied mechanically, a method inwhich the reinforcing fiber bundle is expanded using air flow, and thelike. Examples of methods in which vibration is applied mechanicallyinclude a method in which a reinforcing fiber sheet is brought incontact with vibrating rolls, as described, for example, in JP2015-22799 A. As to the vibration direction, vibration is preferablyapplied in the Y-axis direction (horizontal direction) or the Z-axisdirection (vertical direction), assuming that the running direction ofthe reinforcing fiber sheet is the X-axis. It is also preferable to usea combination of the horizontally vibrating rolls and the verticallyvibrating rolls. In addition, providing a plurality of projections onthe surface of the vibration roll makes it possible to suppress abrasionof the reinforcing fiber on the roll, and accordingly is preferable. Asa method in which air flow is used, for example, a method described inSEN-I GAKKAISHI, vol. 64, P-262-267 (2008) can be used.

<Preheating of Reinforcing Fiber Sheet>

In the present invention, introducing the reinforcing fiber sheet intothe liquid pool after heating the sheet suppresses a decrease in thetemperature of the matrix resin and enhances the viscosity uniformity ofthe matrix resin, and accordingly, is preferable. The reinforcing fibersheet is preferably heated up to or to the vicinity of the temperatureof the matrix resin, and examples of various heating means that can beused for this purpose include air heating, infrared heating,far-infrared heating, laser heating, contact heating, heat mediumheating (steam), and the like. Among others, an infrared heating deviceis easy and convenient and can directly heat the reinforcing fibersheet, and accordingly, can achieve efficient heating up to a desiredtemperature even at a high running speed, and is preferable.

<Matrix Resin>

A matrix resin used in the present invention can be used as a resincomposition containing any of the below-mentioned various resins,particles, hardeners, and further containing any of various kinds ofadditives. A prepreg obtained according to the present invention is in astate in which a reinforcing fiber sheet is impregnated with a matrixresin, and the reinforcing fiber sheet can be directly laminated andmolded as a sheet-like prepreg to afford members composed of FRP. Thedegree of impregnation can be controlled in accordance with the designof the coating section and through an additional-impregnation processcarried out after the matrix resin is applied. A matrix resin cansuitably be selected in accordance with the application, and athermoplastic resin or thermosetting resin is generally used. The matrixresin may be a molten resin melted by heating or a matrix resin which isa matrix resin at room temperature. In addition, the matrix resin may beformed into a solution or varnish using a solvent.

Examples of matrix resins that can be used include matrix resinsgenerally used for FRP, such as thermoplastic resins, thermosettingresins, and photo-curable resins. If these are liquids at roomtemperature, they may be directly used. If they are solids or viscousliquids at room temperature, they may be heated to decrease theviscosity, may be melted to be used as a melt, or may be dissolved in asolvent to be used as a solution or varnish.

Examples of thermoplastic resins that can be used include polymershaving, in the main chain, a bond selected from a carbon-carbon bond, anamide bond, an imide bond, an ester bond, an ether bond, a carbonatebond, a urethane bond, a urea bond, a thioether bond, a sulfone bond, animidazole bond, and a carbonyl bond. Specific examples includepolyacrylate, polyolefin, polyamide (PA), aramid, polyester,polycarbonate (PC), polyphenylenesulfide (PPS), polybenzimidazole (PBI),polyimide (PI), polyetherimide (PEI), polysulfone (PSU),polyethersulfone (PES), polyetherketone (PEK), polyetheretherketone(PEEK), polyetherketoneketone (PEKK), polyaryletherketone (PAEK),polyamideimide (PAI), and the like. In fields requiring heat resistance,such as aircraft applications, PPS, PES, PI, PEI, PSU, PEEK, PEKK, PEAK,and the like are suitable. On the other hand, in industrial andautomobile applications, PA, polyester, PPS, a polyolefin such aspolypropylene (PP), and the like are suitable in order to increasemolding efficiency. These may be polymers, or oligomers or monomers maybe used, because of the low viscosity and low temperature coating.Needless to say, these may be copolymerized depending on the purpose, orvarious kinds of them can be mixed to be used as polymer blends or apolymer alloys.

Examples of thermosetting resins include epoxy resins, maleimide resins,polyimide resins, resins having an acetylene terminal, resins having avinyl terminal, resins having an allyl terminal, resins having a nadicacid terminal, and resins having a cyanate ester terminal. These can beused generally in combination with a hardener or a curing catalyst. Inaddition, these thermosetting resins can suitably be used in mixture.

As thermosetting resins suitable for the present invention, epoxy resinsare suitably used in that epoxy resins have excellent heat resistance,chemical resistance, and mechanical property. In particular, amines,phenols, and epoxy resins whose precursor is a compound having acarbon-carbon double bond are preferable. Specific examples include, butare not limited to: epoxy resins whose precursors are amines, such asvarious isomers of tetraglycidyl diaminodiphenylmethane,triglycidyl-p-aminophenol, triglycidyl-m-aminophenol, andtriglycidylaminocresol; epoxy resins whose precursors are phenols, suchas bisphenol A epoxy resins, bisphenol F epoxy resins, bisphenol S epoxyresins, phenol novolac epoxy resins, and cresol novolac epoxy resins;epoxy resins whose precursors are compounds having a carbon-carbondouble bond, such as alicyclic epoxy resins; and the like. Bromatedepoxy resins resulting from bromating these epoxy resins are also used.Epoxy resins whose precursors are aromatic amines and which are typifiedby tetraglycidyl diaminodiphenylmethane are most suitable for thepresent invention because the epoxy resins have good heat resistance andgood adhesiveness to reinforcing fibers.

Thermosetting resins are preferably used in combination with hardeners.For example, for epoxy resins, a hardener can be used if the hardener isa compound having an active group capable of reacting with an epoxygroup. Preferably, compounds having an amino group, an acid anhydridegroup, or an azido group are suitable. Specifically, various isomers ofdicyandiamide and diaminodiphenyl sulfone are, and amino benzoic acidester types are, suitable. According to specific description,dicyandiamide provides excellent storage stability of prepreg, andaccordingly, is used by preference. In addition, various isomers ofdiaminodiphenyl sulfone afford cured objects having good heatresistance, and accordingly, are most suitable for the presentinvention. As amino benzoic acid ester types, trimethyleneglycoldi-p-aminobenzoate and neopentylglycol di-p-aminobenzoate are used bypreference and have lower heat resistance but have excellent tensilestrength, compared with diaminodiphenyl sulfone, and accordingly, areused selectively in accordance with the application. Needless to say, acuring catalyst can also be used, if necessary. In addition, a hardeneror a curing catalyst and a complexing agent capable of forming a complexcan be used together, from the viewpoint of enhancing the pot life of amatrix resin.

In the present invention, a mixture of a thermosetting resin and athermoplastic resin is also suitably used. A mixture of a thermosettingresin and a thermoplastic resin affords better results than athermosetting resin used singly. This is because a thermosetting resinand a thermoplastic resin have antinomic characteristics: that is, athermosetting resin is generally disadvantageouly brittle but can bemolded at low pressure in an autoclave, and contrarily, a thermoplasticresin is generally advantageously tough but difficult to mold at lowpressure in an autoclave, and accordingly, using these in mixture caneffect a balance between properties and moldability. Such a mixture tobe used preferably contains more than 50 mass % thermosetting resin,from the viewpoint of the mechanical property of FRP obtained by curingprepreg.

<Polymer Particle>

In the present invention, it is also possible to allow the matrix resinor the resin film to contain inorganic particles or organic particles.The type of such inorganic particles can be selected in accordance withthe purpose, and is not limited to any particular type. From the viewpoint of affording electrical conductivity, heat transfer properties,thixotropy, and/or the like, examples of inorganic particles that can besuitably used include carbon-based particles, boron nitride particles,titanium dioxide particles, silicon dioxide particles, and the like. Thetype of such organic particles can also be selected in accordance withthe purpose, and is not limited to any particular type. In particular,use of polymer particles can enhance the toughness, impact resistance,and damping performance of the resulting FRP, and thus, is preferable.In this case, the glass transition temperature (Tg) or meltingtemperature (Tm) of polymer particles which is 20° C. or more higherthan the temperature of a matrix resin makes it easier to retain theform of the polymer particle in the matrix resin, and accordingly ispreferable. The Tg of polymer particles can be measured under thefollowing conditions using a temperature-modulated DSC. As atemperature-modulated DSC device, Q1000 manufactured by TA Instruments,Inc. is suitable, and this can be used on the basis of calibrationcarried out using high-purity indium under a nitrogen atmosphere. Themeasurement conditions can be based on a temperature ramp rate of 2°C./minute, and the temperature-modulation condition can be based on acycle of 60 seconds and an amplitude of 1° C. The reversible componentsare separated from the total heat flow obtained under these conditions,and the temperature at the midpoint of the step signal can be regardedas Tg.

In addition, Tm can be measured using a common DSC at a temperature ramprate of 10° C./minute, and the temperature at the peak top of thepeak-shaped signal corresponding to melting is regarded as Tm.

In addition, the polymer particles are preferably insoluble in a matrixresin, and as such polymer particles, suitable ones described in, forexample, WO2009/142231 as a reference can be used. More specifically,polyamides and polyimides can be preferably used, and polyamides thathave excellent toughness and accordingly can significantly enhance theimpact resistance are most preferable. Examples of polyamides that canbe suitably used include polyamide 12, polyamide 11, polyamide 6,polyamide 66, polyamide 6/12 copolymers, and a polyamide modified tohave a semi IPN (macromolecular interpenetrating network structure) withan epoxy compound (semi IPN polyamide) described in Example 1 ofJP01-104624A. As to the shape of this thermoplastic resin particle, theparticle may be a spherical particle, a nonspherical particle, or aporous particle, and the spherical shape is particularly preferable inthe production method according to the present invention in order not todecrease the resin flow property. In addition, the spherical shape is apreferable aspect in that the spherical shape has no starting point forstress concentration and affords high impact resistance.

Examples of commercially available polyamide particles that can be usedinclude SP-500, SP-10, TR-1, TR-2, 842P-48, 842P-80 (which are allmanufactured by Toray Industries, Inc.), “Orgasol®” 1002D, 2001UD,2001EXD, 2002D, 3202D, 3501D, 3502D (which are all manufactured byArkema K.K.), “Grilamid®” TR90 (manufactured by Emser Werke, Inc.),“TROGAMID®” CX7323, CX9701, CX9704 (manufactured by Degussa AG), and thelike. These polyamide particles may be used singly or in combination oftwo or more kinds thereof.

In addition, polymer particles are preferably retained in the interlayerresin layer in the reinforcing fiber of FRP in order to impart hightoughness to the interlayer resin layer in the reinforcing fiber. Forthis, the number average particle size of the polymer particles ispreferably in the range from 5 to 50 μm, more preferably in the rangefrom 7 to 40 μm, still more preferably in the range from 10 to 30 μm.Having a number average particle size of 5 μm or more makes it possiblethat the particles do not intrude into the reinforcing fiber bundle, butare retained in the interlayer resin layer in the reinforcing fiber ofthe obtained fiber reinforced composite material. Having a numberaverage particle size of 50 μm or less makes it possible that thethickness of the matrix resin layer on the surface of the prepreg ismade suitable, and eventually that the fiber mass content in theobtained FRP is made suitable.

<Viscosity of Matrix Resin>

A matrix resin used in the present invention preferably has an optimalviscosity selected from the viewpoint of processability and stability.Specifically, it is preferable to have a viscosity in the range from 1to 60 Pa·s because such a viscosity makes it possible that a drip of theliquid at the outlet of the narrowed section is suppressed and that thehigh-speed running properties and stable running properties of thereinforcing fiber sheet are enhanced. As used herein, a viscosity refersto one measured at a strain rate of 3.14 s⁻¹ at a matrix resintemperature in the liquid pool. As a measurement device, aviscoelasticity measurement device such as of a parallel disc type or aconical type can be used. The viscosity of the matrix resin is morepreferably 5 to 30 Pa·s.

<Application Step of Matrix Resin>

Taking a UD base material for an example of a reinforcing fiber sheet,an application step of a matrix resin will be described with referenceto FIG. 1. The method of providing the reinforcing fiber sheet 1 b withthe matrix resin 2 in the coating device 100 according to theillustration in FIG. 1 is a method in which a plurality of thereinforcing fibers 1 a unwound from the creels 11 are arrangedunidirectionally (in the depth direction of the page) through thearrangement device 13 to obtain the reinforcing fiber sheet 1 b, andthen, the reinforcing fiber sheet 1 b is allowed to pass through thecoating section 20 in the horizontal direction to provide both faces ofthe reinforcing fiber sheet 1 b with the matrix resin 2. Thus, a primaryimpregnate prepreg 1 c can be obtained. Needless to say, the primaryimpregnate prepreg itself also corresponds to a prepreg mentioned in thepresent invention. Here, the horizontal direction is indicated as thedirection X in FIG. 1. In the present invention, the reinforcing fibersheet can be allowed to pass in the slanting direction, or the slantingrunning direction and the horizontal running direction can be combined,as below-mentioned. The slanting direction refers to a directionintermediate between the horizontal direction and the verticaldirection. More specifically, the horizontal direction or the slantingdirection can be defined as being within the range of from −80° to +80°with respect to 0° as the horizontal plane. Defining the runningdirection of the reinforcing fiber sheet in the narrowed section in thecoating section as a range of from −30° to +30° with respect to 0° asthe horizontal plane makes it possible to incorporate such a device intoan existing prepreg production apparatus, and thus, is preferable fromthe viewpoint of the versatility of facilities. The running direction ofthe reinforcing fiber sheet in the narrowed section in the coatingsection is more preferably −15° to +15° with respect to 0° as thehorizontal plane. In the below-mentioned FIG. 29 and others, thereinforcing fiber sheet is described as being introduced into thecoating section in the slantingly downward direction, and in addition,being allowed to run in the vertically slanting direction when runningthrough the diverting members in the coating section, but the runningdirection of the reinforcing fiber sheet is horizontal in the portionwhose cross-sectional area decreases continuously and in the narrowedsection. In addition, introducing the reinforcing fiber sheet 1 bhorizontally with respect to the coating section 20, as in FIG. 1,causes the running pathway of the reinforcing fiber sheet 1 b to belinearized, thus making it more unlikely to generate disturbance in thereinforcing fiber sheet 1 b depending the thickness of the reinforcingfiber sheet 1 b, and thus, is preferable. In such a case, it ispreferable to have a sealing mechanism so that the matrix resin 2 cannotleak out through a portion at which the reinforcing fiber sheet 1 b isintroduced into the coating section 20.

The coating section 20 includes outlet side members 29 opposed to eachother and having a predetermined gap D therebetween, and also includeswall constituent members 21 a and 21 b at the introduction side for thereinforcing fiber sheet 1 b and the outlet side members 29 at the outletside. A liquid pool 22 and a slit-like narrowed section 23 are formedbetween an upper-side member 24 and a lower-side member 25, wherein thenarrowed section is positioned on the outlet side of the liquid pool 22and has a smaller cross-sectional area than the largest cross-sectionalarea of the liquid pool 22.

In the coating section 20, the reinforcing fiber sheet 1 b introducedinto the liquid pool 22 runs in the horizontal direction, and, at thesame time, is accompanied by the matrix resin 2 surrounding thereinforcing fiber sheet. During this, the accompanying matrix resin 2 isgradually compressed in the portion 22 b whose cross-sectional area inthe liquid pool 22 decreases continuously in the running direction ofthe reinforcing fiber sheet 1 b, and thus, the pressure of the matrixresin 2 increases toward the outlet of the liquid pool 22. When thepressure in the outlet region of the liquid pool 22 increases, it ismore difficult for the accompanying liquid flow to flow toward theoutlet any further, and the accompanying liquid flows toward theupper-side member 24 and the lower-side member 25, and then impeded bythe upper-side member 24 and the lower-side member 25, resulting inflowing in the direction opposite to the running direction of thereinforcing fiber sheet 1 b. As a result, a circular stream T is formedalong the plane of the reinforcing fiber sheet 1 b and the wall surfacesof the upper-side member 24 and the lower-side member 25 in the liquidpool 22. Thus, even if the sheet-like reinforcing fiber 1 b brings fuzzin the liquid pool 22, the fuzz moves along the circular stream T, andcannot approach the outlet region of the liquid pool 22, where theliquid pressure is higher, or the narrowed section 23. When thereinforcing fiber sheet 1 b is run at a high speed, the liquid pressurefurther increases, and accordingly, further enhances the effect ofpreventing the fuzz from approaching the outlet region and the narrowedsection 23. As a result, this makes it possible to provide thereinforcing fiber sheet 1 b with the matrix resin 2 at a higher speed,and enhances productivity significantly.

In addition, the increased liquid pressure has the effect of making iteasier for the reinforcing fiber sheet 1 b to be impregnated with thematrix resin 2. This is based on the property (Darcy's law) according towhich the degree at which a porous object such as a reinforcing fiberbundle is impregnated with a matrix resin is increased by the pressureof the matrix resin. This can also enhance the impregnation effectbecause running the reinforcing fiber sheet 1 b at a higher speedincreases the liquid pressure further. In this regard, the reinforcingfiber sheet 1 b is impregnated with the matrix resin 2 throughgas-liquid replacement with bubbles remaining in the reinforcing fibersheet 1 b, and the above-mentioned circular stream T and the ascendingforce cause the bubbles to gather more on or near the boundary betweenthe portion 22 a whose cross-sectional area does not decrease and theportion 22 b whose cross-sectional area decreases continuously. Becauseof this, a degassing mechanism 26 for degassing the bubbles from thematrix resin 2 is preferably disposed in this vicinity. Morespecifically, the position at which the degassing mechanism is disposedis preferably in the range of 5 cm or less from the boundary between theportion 22 a whose cross-sectional area does not decrease and theportion 22 b whose cross-sectional area decreases continuously. In thisregard, Patent Literature 3 describes an impregnation process carriedout with a plurality of fixed guides, conceivably causing bubbles to begenerated over a broad range, and a degassing mechanism is notnecessarily disposed in the vicinity of the guides, posing thepossibility that the bubbles are not sufficiently removed.

Further, the increased liquid pressure allows the reinforcing fibersheet 1 b to be automatically aligned with the center of the gap D, andthe reinforcing fiber sheet 1 b is not directly abraded against the wallsurfaces of the liquid pool 22 and the narrowed section 23, whereby theeffect of suppressing the generation of fuzz here is also achieved. Thisis because, when any external disturbance or the like causes thereinforcing fiber sheet 1 b to approach either side in the gap D, thematrix resin 2 is pushed and compressed in the resulting narrower gap onthe approached side, and accordingly, the liquid pressure furtherincreases on the approached side, pushing the reinforcing fiber sheet 1b back to the center of the gap D.

The narrowed section 23 is designed to have a smaller cross-sectionalarea than the largest cross-sectional area of the liquid pool 22. Asunderstood from FIG. 1, the smaller cross-sectional area is simply dueto the fact that the length in the direction perpendicular to thepseudo-plane of the reinforcing fiber sheet 1 b is smaller, that is, thedistance between the members is narrower. This is intended to achievethe impregnation and the automatic alignment effect through increasingthe liquid pressure in the narrowed section 23 as above-mentioned. Inaddition, the cross-sectional shape of the inlet of the narrowed section23 is preferably made to conform to the cross-sectional shape of thatface of the liquid pool 22 which is in contact with the inlet, from theviewpoint of the running properties of the reinforcing fiber sheet 1 band the flow control of the matrix resin 2, but, if necessary, thecross-sectional shape of the inlet of the narrowed section 23 may bemade slightly larger.

In this respect, the reinforcing fiber sheet 1 b in the coating section20 in FIG. 1 runs in the completely horizontal direction, but, withoutlimitation to this, may run in the slanting direction in the coatingsection 20 to the extent that the fuzz collection effect and the bubblesdischarge effect can be obtained, and that the reinforcing fiber sheet 1b can run stably and continuously. Alternatively, it is possible toslant the coating section 20.

In addition, the total amount of the matrix resin 2 applied to thereinforcing fiber sheet 1 b can be controlled in the gap D in thenarrowed section 23. For example, in cases where the total amount of thematrix resin 2 applied to the reinforcing fiber sheet 1 b is desired tobe larger (the areal weight is desired to be larger), it is onlynecessary to make an adjustment to widen the gap D.

FIG. 1 depicts one reinforcing fiber sheet being introduced into thecoating section in the horizontal direction, but the introduction of thereinforcing fiber sheet into the coating section is not limited to this.If necessary, a plurality of reinforcing fiber sheets may be introduced,and the introduction direction may be slanting. This will be describedwith reference to FIGS. 2 to 4.

In FIG. 2, one reinforcing fiber sheet 1 b runs from above in theslantingly downward direction, and is introduced into the coatingsection 20 through the opening 30. Then, the running direction of thereinforcing fiber sheet 1 b is diverted to the horizontal direction by adiverting member 31, and withdrawn through the narrowed section 23.Introducing the reinforcing fiber sheet in the slantingly downwarddirection through the upper portion of the coating section is aconvenient method that can prevent the matrix resin stored in thecoating section from leaking, and thus, is preferable. Specifically,disposing the opening 30 in the upper portion of the coating sectioneliminates the necessity to provide a special sealing mechanism, thusmaking it possible to simplify the device. Obviously, it is alsopossible to include a sealing mechanism at the opening in accordancewith the various cases of necessity, for example, filling the liquidpool with inert gas. In addition, the diverting member 31 preferably hasa structure at least such that the face thereof brought in contact withthe reinforcing fiber sheet 1 b is curved. In addition, the divertingmember 31 is preferably fixed from the viewpoint of preventing thereinforcing fiber sheet 1 b from winding around. Taking these intoconsideration, the diverting member 31 is preferably a fixed bar havinga curved face, and examples of the cross-sectional shape of the memberinclude a circle, ellipse, saddle shape, and the like. In addition, theportion at which the diverting member 31 is brought in contact with thereinforcing fiber sheet 1 b may have a curved face and a plane face inmixture, and having a curved face at the starting part and ending partof contact with the reinforcing fiber sheet 1 b makes it possible toinhibit fuzz generation, and thus, is preferable. Furthermore,particularly in cases where the running speed is made higher, thediverting member 31 can also be a rotatable roller from the viewpoint ofinhibiting the reinforcing fiber sheet 1 b from chafing against thediverting member 31.

In addition, the reinforcing fiber sheet 1 b is pressed against thediverting member 31, and thus, in some cases, the gas in the reinforcingfiber sheet 1 b is replaced with the matrix resin 2, whereby the sheetis impregnated. In particular, as shown in FIG. 4, pressing the sheetagainst a plurality of diverting members 31 at angles makes it possibleto advance impregnation efficiently.

In addition, the position at which the diverting member 31 is disposedis preferably 1 cm or more toward the portion 22 a whose cross-sectionalarea does not decrease and from the boundary between the portion 22 awhose cross-sectional area does not decrease and the portion 22 b whosecross-sectional area decreases continuously, from the viewpoint of notimpeding the circular stream T.

In FIG. 3, two reinforcing fiber sheets 1 b run from above in theslantingly downward direction, and are introduced into the coatingsection 20 through the opening 30. Then, the running direction of thetwo reinforcing fiber sheets 1 b is diverted to the horizontal directionby the diverting members 31, and the two sheets are laminated and thenwithdrawn through the narrowed section 23. When this takes place, thetwo reinforcing fiber sheets 1 b are laminated with the matrix resin 2contained therebetween, making it easier to advance impregnation in theportion 22 b whose cross-sectional area decreases continuously and inthe narrowed section 23, and thus, is preferable.

In addition, the further the reinforcing fiber sheets 1 b laminated withthe matrix resin 2 sandwiched therebetween move toward the outlet, thehigher the liquid pressure in the portion 22 b whose cross-sectionalarea decreases continuously, and thus, the further the impregnation withthe matrix resin 2 is advanced, causing the surplus matrix resin 2 to besqueezed out of the reinforcing fiber sheet 1 b laminate, and making itpossible to inhibit the laminate from swelling excessively in the thickdirection. This makes it possible that the reinforcing fiber sheet 1 blaminate is withdrawn through the narrowed section 23 without gettingstuck in the thickness direction. This effect is remarked particularlywhen the running speed is high. For this purpose, it is important thatthe liquid pressure is gradually increased in the portion 22 b whosecross-sectional area decreases continuously. More specifically, thelength H of the portion 22 b whose cross-sectional area decreasescontinuously is preferably 10 mm or more, more preferably 30 mm or more,from the viewpoint of inhibiting the reinforcing fiber sheet 1 blaminate from swelling excessively in the thick direction. If theportion 22 b whose cross-sectional area decreases continuously does notexist, the reinforcing fiber sheet 1 b laminate containing the matrixresin 2 therein and having an excessive swell in the thick direction isintroduced into the narrowed section 23 rapidly, and thus, the surplusmatrix resin 2 cannot be discharged out, and causes the laminate toeasily get stuck in cases where the laminate is thicker than the spacingof the gap D. In addition, if the length H of the portion 22 b whichdecreases continuously is less than 10 mm, the thickness of thereinforcing fiber sheet 1 b laminate can be decreased in cases where therunning speed of the reinforcing fiber sheet 1 b is sufficiently low,but in cases where the running speed is made higher, the effect isinsufficient, still making it more likely that the laminate gets stuck.As above-mentioned, the length H of 30 mm or more makes it possible toincrease the running speed up to 20 m/minute or more.

In addition, the length C (see FIG. 14) of the liquid pool can beshortened in a range which enables the reinforcing fiber sheet to run,and specifically, the length is preferably 400 mm or less from theviewpoint of decreasing the volume of the liquid pool. It is morepreferably 200 mm or less.

In FIG. 4, two reinforcing fiber sheets 1 b run from above in theslantingly downward direction, and are introduced into the coatingsection 20 through the opening 30. Then, the two reinforcing fibersheets 1 b are each impregnated while passing through a plurality ofdiverting members 31, and finally, the two sheets are laminated and thenwithdrawn through the narrowed section 23. In such a case, the shape andnumber of the diverting members 31 for advancing impregnation can beselected variously in accordance with the purpose. In addition, thecontact length between the diverting member 31 and the reinforcing fibersheet 1 b and the angle (wrap angle) formed between both ends of thecontact portion and the center of the diverting member 31 can beselected in accordance with the purpose.

FIGS. 3 and 4 show an example in which two reinforcing fiber sheets 1 bare used, but obviously, the number of sheets can be optionally 3 ormore.

FIG. 5 is a view of the coating section 20, as viewed in the directionopposite to X in FIG. 1. In the coating section 20, side wall members 32are provided to prevent the matrix resin 2 from leaking by both ends ofthe reinforcing fiber sheet 1 b in the arrangement direction, and theoutlet 28 of the narrowed section 23 is formed in the space surroundedby the outlet side members 29 and the side wall members 32. Here, theoutlet 28 is slit-like, and the cross-sectional aspect ratio (U/D inFIG. 5) may be set in accordance with the shape of the reinforcing fibersheet 1 b which is desired to be provided with the matrix resin 2.

FIG. 6 is a cross-sectional view depicting the structure of the insideof the coating section 20, as viewed in the direction Z. Here, theupper-side member 24 is omitted so that the drawing can be easier tosee.

FIG. 7 depicts the circular stream of the matrix resin 2 in theclearance gap 33 between the reinforcing fiber sheet 1 b and the sidewall member 32. When the clearance gap 33 between the reinforcing fibersheet 1 b and the side wall member 32 is large, a circular stream in theedge is generated in the direction of R in the matrix resin 2. In theliquid pool 22, this circular stream R in the edge becomes an outwardflow (Ra) on or near the boundary between the portion 22 b whosecross-sectional area decreases continuously and the narrowed section 23,and accordingly, the circular stream flows in the direction which causesthe reinforcing fiber sheet to be torn apart (causing splits in thesheet-like reinforcing fiber bundles), in cases where the reinforcingfiber sheet is formed of arranged reinforcing fiber bundles (sheet-likereinforcing fiber bundles). This causes the distance between thereinforcing fibers to be expanded, thus posing the possibility thatarrangement nonuniformity is caused in the reinforcing fibers in theresulting prepreg. On the other hand, the circular stream R in theliquid pool 22 becomes an inward flow (Rb) on or near the boundarybetween the portion 22 a whose cross-sectional area does not decreaseand the portion 22 b whose cross-sectional area decreases continuously,and accordingly, the reinforcing fiber sheet 1 b is compressed in thewidth direction, resulting in edge folding of the reinforcing fibersheet in some cases. In a device, such as typified by Patent Literature2 (JP3252278B2), for coating both faces of an integrated sheet-like basematerial (particularly, a film) with a matrix resin, such a circularstream as caused in the edge in the clearance gap 33 between thereinforcing fiber sheet 1 b and the side wall member 32 affects thequality insignificantly, and accordingly, has attracted no attention.

In view of this, it is important in the present invention to carry outwidth regulation for decreasing the clearance gap 33 between thereinforcing fiber sheet 1 b and the side wall member 32 to inhibit thegeneration of the circular stream in the edge. Specifically, it isimportant that the width L in the direction Y of the portion 22 b whosecross-sectional area decreases continuously in the liquid pool 22, thatis, the distance L between the right and left side wall members 32 isadapted to satisfy the relationship of the below-mentioned Formula (1)with the width W of the reinforcing fiber sheet 1 b measured at theoutlet of the narrowed section 23.

L≤W+10 (mm)  (1)

That is, the spacing L (the width of the end of the liquid pool;however, the width of the end of the liquid pool in cases where thosefaces of the right and left side wall members which form the liquid poolare not parallel) between the right and left side wall members 32 andthe width W of the sheet-like reinforcing fiber bundle at the outlet ofthe narrowed section are made to satisfy the relationship of theabove-mentioned Formula (1).

This suppresses the generation of a circular stream in the edge andmakes it possible to suppress split and edge folding of the reinforcingfiber sheet 1 b and to obtain the prepreg 1 d in which the reinforcingfibers are uniformly arranged over the full width (W) of the prepreg 1 band which is of high grade and has high stability. Furthermore, thistechnology applied to a prepreg can not only enhance the grade andquality of the prepreg but also enhance the mechanical property andquality of FRP obtained using the prepreg. The relationship between Land W is more preferably L≤W+2 (mm), and thus, the split and edgefolding of the reinforcing fiber sheet can further be suppressed.

In addition, it is preferable to make adjustments so that the lowerlimit of L is equal to or greater than W−5 (mm), from the viewpoint ofenhancing the uniformity of the dimension in the width direction of theprepreg 1 d.

In this regard, this width regulation is preferably positioned at leastat G (FIG. 6) on the outlet side of the portion 22 b whosecross-sectional area decreases continuously, from the viewpoint ofsuppressing the generation of the circular stream R in the edge due to ahigh liquid pressure on the outlet side of the portion 22 b whosecross-sectional area decreases continuously. Furthermore, this widthregulation is more preferably provided in the whole region of theportion 22 b whose cross-sectional area decreases continuously, morepreferably in the whole region of the liquid pool 22, whereby thegeneration of the circular stream R in the edge can be suppressedsubstantially completely, and, as a result, the splitting and edgefolding of the reinforcing fiber sheet can be suppressed substantiallycompletely.

In addition, the width regulation may be provided only in the liquidpool 22 if it is provided only from the viewpoint of suppressing thecircular stream in the edge in the clearance gap 33 between thereinforcing fiber sheet 1 b and the side wall member 32, but it ispreferable to provide the width regulation also to the narrowed section23 in the same way, from the viewpoint of suppressing excessiveapplication of the matrix resin 2 to the sides of the primary impregnateprepreg 1 c.

<Width Regulation Mechanism>

The above-mentioned has described a case where the side wall members 32serve for the purpose of width regulation, but, as shown in FIG. 8, itis also possible to provide width regulation mechanisms 34 a and 34 bbetween the side wall members 32 and to provide width regulation usingsuch mechanisms. This is preferable because the capability to freelychange the width regulated by the width regulation mechanisms makes itpossible to use one coating section to produce different prepregs havingvarious widths. Here, the relationship between the width (W) of thereinforcing fiber sheet 1 b at the outlet of the narrowed section 23 andthe width (L2) regulated by the width regulation mechanisms at theoutlet side end of the width regulation mechanisms is preferably L2≤W+10(mm), more preferably L2≤W+2 (mm). In addition, it is preferable to makeadjustments so that the lower limit of L2 is equal to or greater thanW−5 (mm), from the viewpoint of enhancing the uniformity of thedimension in the width direction of the prepreg 1 d.

In cases where a width regulation mechanism is used, L in theabove-mentioned Formula (1) is regarded as L2.

The shape and material of the width regulation mechanism are each notlimited to a particular one, and a plate-like bush type is easy andconvenient, and accordingly, preferable. In addition, allowing the widthregulation mechanism to have a width slightly smaller than the distancebetween the upper-side member 24 and the lower-side member 25 (as seenin FIG. 8, the width refers to the vertical length of the widthregulation mechanisms 34 a and 34 b in the view “viewed in the directionX”) is preferable because such a width makes it possible not to impedethe horizontal flow of the matrix resin 2. On the other hand, the shapefrom the middle portion to the outlet side end of the width regulationmechanism is preferably in conformity to the internal shape of theliquid pool 22 because such conformity makes it possible to suppress theretention of the matrix resin 2 in the liquid pool and suppress thedegradation of the matrix resin 2. In this sense, the width regulationmechanism 34 is preferably inserted into the narrowed section 23. FIG. 8shows an example of a plate-like bush as the width regulation mechanism,and shows an example in which the width regulation mechanism is insertedinto the narrowed section 23, and in which the portion from the middleof the bush toward the outlet side conforms to the tapered shape of theportion 22 b whose cross-sectional area decreases continuously. FIG. 8shows an example in which L2 is constant to the outlet from the boundaryregion between the portion 22 a whose cross-sectional area does notdecrease and the portion 22 b whose cross-sectional area decreasescontinuously, but the width to be regulated may vary depending on thesite to the extent that the purpose of the width regulation mechanism isfulfilled. The width regulation mechanism can be fixed in the coatingsection 20 by an arbitrary method, and fixing the mechanism of aplate-like bush type at a plurality of sites in the running direction ofthe reinforcing fiber sheet 1 b can make it possible to suppressvariation of the regulation width due to the deformation of theplate-like bush caused by a high liquid pressure.

<Shape of Liquid Pool>

As described above in detail, it is important in the present inventionthat allowing the cross-sectional area to decrease continuously in therunning direction of the reinforcing fiber sheet 1 b in the liquid pool22 increases the liquid pressure in the running direction of reinforcingfiber sheet, and here, the shape of the cross-sectional area decreasingcontinuously in the running direction of the reinforcing fiber sheet isnot limited to a particular one as long as the shape allows the liquidpressure to increase continuously in the running direction. The shapemay be a tapered (linear) one or show a curved form such as a trumpetshape in the cross-sectional view of the liquid pool. In addition, thecross-sectional area decreasing portion may be continuous over the fulllength of the liquid pool, or the liquid pool may contain a part inwhich the cross-sectional area does not decrease or contrarilyincreases, to the extent that the object and effect of the presentinvention can be achieved. These will be described in detail below withreference to FIGS. 9 to 12. Here, FIGS. 9 to 12 show the outlet region,and the region at which the reinforcing fiber sheet 1 b is introducedand a degassing mechanism are omitted.

FIG. 9 is a detailed cross-sectional view of the coating section 20 inFIG. 1. In cases where the portion 22 b whose cross-sectional areadecreases continuously in the liquid pool 22 is tapered, the smaller theopening angle θ of the taper, the more preferable, and specifically, theangle is preferably an acute angle (90° or less). 0 is more preferably30° or less. This makes it possible that the effect of compressing thematrix resin 2 in the portion 22 b (tapered portion) whosecross-sectional area decreases continuously in the liquid pool 22 isenhanced, and that a high liquid pressure is made easier to obtain.

FIG. 10 is a detail cross-sectional view of the coating section 20 baccording to an embodiment other than in FIG. 9. The coating section 20b is the same as the coating section 20 in FIG. 9 except that theportion 22 b whose cross-sectional area decreases continuously is in theform of a two-tier taper. In this manner, the portion 22 b whosecross-sectional area decreases continuously in the liquid pool 22 may beconstituted by a multi-tier tapered portion composed of two or moretiers. In this respect, the opening angle θ of the tapered portionnearest the narrowed section 23 is preferably an acute angle, from theviewpoint of enhancing the above-mentioned compression effect. Also inthis case, the length H of the portion 22 b whose cross-sectional areadecreases continuously in the liquid pool 22 is preferably 10 mm ormore. The length H of the portion 22 b whose cross-sectional areadecreases continuously is more preferably 30 mm or more. Having amulti-tier tapered portion as the portion 22 b whose cross-sectionalarea decreases continuously in the liquid pool 22, as in FIG. 10, makesit possible to maintain the volume of the matrix resin 2 that can bestored in the liquid pool 22, and at the same time, to decrease theangle θ of the tapered portion nearest the narrowed section 23. Thisincreases the liquid pressure caused at the outlet of the liquid pool22, and can further enhance the fuzz elimination effect and theimpregnation effect of the matrix resin 2.

FIG. 11 is a detailed cross-sectional view of the coating section 20 caccording to an embodiment other than in FIG. 9. The coating section 20c is the same as the coating section 20 in FIG. 9 except that theportion 22 b whose cross-sectional area decreases continuously is in theform of tiers. In this manner, allowing the portion nearest the outletof the liquid pool 22 to have the portion 22 b whose cross-sectionalarea decreases continuously makes it possible to obtain the effect ofincreasing the liquid pressure, wherein the effect is an object of thepresent invention, and accordingly, the other part of the liquid pool 22may include a portion 22 c whose cross-sectional area decreasesintermittently.

FIG. 12 is a detailed cross-sectional view of the coating section 20 daccording to an embodiment other than in FIG. 9. The coating section 20d is the same as the coating section 20 in FIG. 9 except that theportion 22 b whose cross-sectional area decreases continuously is in theform of a trumpet (a curve). In the coating section 20 in FIG. 9, theportion 22 b whose cross-sectional area decreases continuously in theliquid pool 22 is tapered (linear), but, without limitation to this, maybe, for example, in trumpet shape (curved shape) as in FIG. 12. However,the portion 22 b whose cross-sectional area decreases continuously andthe narrowed section 23 are preferably connected smoothly. This isbecause any step at this boundary causes the reinforcing fiber sheet 1 bto be caught by the step, where fuzz will undesirably be generated. Incases where, in this manner, the portion 22 b whose cross-sectional areadecreases continuously in the liquid pool 22 is in trumpet shape, theopening angle θ between the virtual tangent lines on the portionsnearest to the outlet of the portion 22 b whose cross-sectional areadecreases continuously in the liquid pool 22 is preferably an acuteangle.

In this regard, the above description illustrates an example in whichthe cross-sectional area decreases smoothly, but the cross-sectionalarea of the liquid pool in the present invention does not necessarilyneed to decrease smoothly, to the extent that the object of the presentinvention is not impaired.

FIG. 13 is a detailed cross-sectional view of the coating section 40according to an embodiment other than of the present invention.Differently from an embodiment of the present invention, the liquid pool41 in FIG. 13 does not contain a portion whose cross-sectional areadecreases continuously in the running direction (direction X) of thereinforcing fiber sheet, but the liquid pool is configured such that thecross-sectional area decreases discontinuously and suddenly at theboundary 42 with the narrowed section 23. This makes it more likely thatthe reinforcing fiber sheet 1 b causes clogging.

In cases where the matrix resin stored in the liquid pool is likely toalter owing to heat or the like, the volume of the liquid pool ispreferably as small as possible from the viewpoint of the qualitystability of the resulting prepreg and the process stability forcoating. On the other hand, in cases where the volume of the liquid poolis excessively small, it is assumed that the supply of the matrix resininto the liquid pool is more likely to be insufficient with respect tothe application amount. Such a case poses the possibility that thecircular stream in the liquid pool will become ununiform, causing therunning properties of the reinforcing fiber sheet to be poor. Heatingthe whole coating section causes a gap between the upper-side member 24and the liquid surface in the liquid pool 22, and thus causes thetemperature of the matrix resin 2 to be ununiform, posing thepossibility that the quality stability of the resulting prepreg and theprocess stability for coating will be poor. Because of this, it ispreferable to keep a balance among making the volume of the liquid poolsmall, the supply amount of the matrix resin into the liquid pool, andthe application amount of the matrix resin. From this viewpoint, it ispreferable to make the volume of the liquid pool small and provide astorage portion 43 for the matrix resin 2 in the vicinity of the opening30, as with, for example, the coating section 20 e depicted in FIG. 14.In addition, making the shape of this storage portion 43 vertically longmakes it easy to detect the liquid surface 44 of the matrix resin 2 andalso makes it easy to control the storage amount of the matrix resin 2by controlling the liquid surface. Feeding the position of the liquidsurface back to a matrix resin supply system makes it possible to keep abalance between the supply amount of the matrix resin into the liquidpool and the application amount of the matrix resin. Because of this,the storage portion 43 can be formed, for example, by the wallconstituent member 21 and the upper-side member 24, but is not limitedto this. From the viewpoint of minimizing the storage amount of thematrix resin, the distance B defined by the lower face of the upper-sidemember 24 and the upper face of the storage portion 43 in FIG. 14 ispreferably 100 mm or less, and preferably 50 mm or less, alsoconsidering the degree of flexibility in designing the running pathwayof the reinforcing fiber sheet 1 b.

In addition, it is preferable to add a mechanism that removes fuzz fromthe reinforcing fiber sheet in the coating section. Furthermore, it isalso preferable to add a mechanism that discharges the surplus matrixresin out.

<Application Steps of Resin Film and Release Sheet>

In the present invention, a resin film or a release sheet can further beapplied to the above-mentioned primary impregnate prepreg 1 c withdrawnfrom the application step of a matrix resin. FIG. 1 shows an example inwhich the resin film 4 is applied to one face and that the release sheet3 is applied to the other face. In this example, the resin film 4 issupplied from the supply device 16 b, the release sheet 3 is suppliedform the supply device 16 a, and the film and the sheet can be laminatedonto a primary impregnate prepreg 1 c on the conveyance rolls 15. FIG. 1shows an example in which the resin film 4 and the release sheet 3, oneeach, are laminated, but in accordance with the purpose, only the resinfilm 4 or only the release sheet 3 may be laminated in one aspect, resinfilms may be laminated on both faces in another aspect, or releasesheets may be laminated on both faces in another aspect. In anotheraspect, a release sheet and a resin film may be laminated on each other.The type of a resin which forms a resin film can be selected suitably inaccordance with the purpose, and a mixture of a plurality of types ofresins may form the resin film. In addition, in cases where two resinfilms are used, they may be the same kind of resin film or differentkinds of resin films. In addition, in cases where two release sheets areused, they may be the same type of release sheet or different types ofrelease sheets.

On the other hand, examples of release sheets that can be suppliedinclude sheets formed of a polymer having releasability and sheets inwhich a release layer is provided on a base material, for example,sheets in which a release layer is laminated on the above-mentionedresin film. Obviously, the above description is not limited to theaspect in FIG. 1, and can equally apply to the aspects in the otherdrawings.

In the present invention, a resin used for the resin film is not limitedto any particular one, and can suitably be selected in accordance withthe purpose. A resin to be used for the resin film may be a singleresin, or can be a blend of different kinds of polymers or a resincomposition which is a blend of different components. The resin film tobe used here can contain the above-mentioned particles. In theabove-mentioned coating step, use of a matrix resin containing particlesis more likely to increase the viscosity, and in some cases, decreasesthe coating uniformity while the reinforcing fiber sheet is running at ahigh speed. Because of this, providing particles in the application stepof a resin film enhances the high-speed running stability of thereinforcing fiber sheet in the coating step, and thus, is preferable. Inthis case, the resin film containing particles can be a resin filmcomposed of a matrix resin. This is efficient because it makes itpossible to provide particles independent of the coating step and, atthe same time, provide a matrix resin. In this case, the matrix resin ofthe matrix resin containing particles may be the same as or differentfrom the matrix resin component used in the coating step. The componentsof a matrix resin used in the coating step and a matrix resin to beformed into a resin film can be adjusted taking into consideration thehigh-speed running stability in the coating step and the pot life ofstorage in the coating section.

Alternatively, a resin component can be taken out of a matrix resin, andformed into a resin film. For example, in the case of FRP, athermoplastic resin is blended with a matrix resin composed mainly of athermosetting resin so that the resin toughness can be enhanced, but insome cases, the thermoplastic resin increases the viscosity of thematrix resin. In such a case, this thermoplastic resin is not used as acomponent of the matrix resin to be provided in the above-mentionedcoating step and can be applied as a resin film to a primary impregnateprepreg so that the coating stability can be enhanced. Such athermoplastic resin to be used is often PES, PEI, PI, or the like. Insome cases, such a thermoplastic resin film can also be aself-supporting film that needs no support, and is useful from theviewpoint of the possibility of omitting such a support.

A method of obtaining a resin film is not limited to any particularmethod, and a known method can be used. Such a film can be formed, forexample, using any of various known coaters such as roll coaters, commacoaters, knife coaters, die coaters, and spray coaters. If necessary, asupport such as a release sheet can be coated with a resin to form afilm.

<Running Mechanism>

Known rollers or the like can suitably be used as a running mechanismfor conveying a reinforcing fiber sheet and the prepreg according to thepresent invention. In the present invention, the reinforcing fiber sheetis conveyed horizontally or slantingly, and accordingly, the rollers arepreferably disposed before and after the coating section, which isbetween the rollers.

In addition, it is preferable in the present invention that the runningpathway of the reinforcing fiber sheet is as linear as possible in orderto suppress arrangement disturbance and fuzzing of the reinforcingfibers. In addition, the prepreg is often a sheet-like integrated objectthat is a laminate containing a release sheet, and it is preferable thatthe running pathway of the sheet-like integrated object is also aslinear as possible, because a bend existing in a conveying step of theobject generates wrinkles due to a perimeter difference between theinner layer and the outer layer in some cases. From this viewpoint, niprolls are more preferably used in the running pathway of the sheet-likeintegrated object.

Which of S-shaped arranged rolls and nip rolls should be used cansuitably be determined in accordance with the production conditions andthe product characteristics.

<High Tension Take-Up Device>

In the present invention, it is preferable that a high tension take-updevice for withdrawing the prepreg from the coating section is disposeddownstream of the coating section in the process. This is because highfriction force and shearing stress are generated between the reinforcingfiber sheet and the matrix resin in the coating section, andaccordingly, it is preferable that high take-up tension is generateddownstream in the process, in order to overcome the high friction forceand the shearing stress and withdraw the prepreg. Examples of hightension take-up devices that can be used include nip rolls, S-shapedarranged rolls, belting presses, and the like. In any case of these,enhancing friction force between the device and the prepreg can preventslipping and achieve stable running. To achieve this, it is preferableto arrange a high friction coefficient material on the surface of thedevice, or to increase the pressing pressure against the prepreg. Fromthe viewpoint of preventing slipping, belting press is reliable. On theother hand, the S-shaped arranged rolls make it possible to more easilycontrol friction force on the basis of the roll diameter and the contactlength, and accordingly, are preferable.

<Release Sheet Supply Device and Winder>

A release sheet supply device and a winder can suitably be used inproducing prepreg or FRP using the present invention. As such a device,any known one can be used, and in any case, it is preferable from theviewpoint of running the sheet stably that such a device includes amechanism for making it possible to feed an unwinding or wind-up tensionback to the unwinding or wind-up speed.

<Additional-Impregnation>

In order to make adjustments to a desired degree of impregnation, it ispossible to further combine, with the present invention, a means forfurther enhancing the degree of impregnation using an impregnationdevice separately after coating. Here, to distinguish this means fromthe impregnation in the coating section, such an impregnation processadditionally carried out after coating is referred to as anadditional-impregnation process, and a device for anadditional-impregnation process is referred to as anadditional-impregnation device. A device used as anadditional-impregnation device is not limited to a particular one, andcan suitably be selected from known ones in accordance with the purpose.For example, as described in JP2011-132389A and WO2015/060299,impregnation can be promoted by preheating a laminate of a sheet-likecarbon fiber bundle and a resin on a hot plate and sufficientlysoftening the resin on the sheet-like carbon fiber bundle, followed byusing a device for pressing with nip rolls which are also heated. Thehot plate temperature and nip roll surface temperature for preheating,the linear pressure of the nip rolls, and the diameter and number of thenip rolls can suitably be selected so as to achieve a desired degree ofimpregnation. Alternatively, it is also possible to use such “S-wraprolls” as described in WO2010/150022, wherein a prepreg sheet runs inS-shape through the S-wrap rolls. In the present invention, “S-wraprolls” are simply referred to as “S-shaped arranged rolls”. FIG. 1 inWO2010/150022 describes an example in which a prepreg sheet runs inS-shape, but the contact length between the sheet and the roll may beadjusted in U-shape, V-shape, or A-shape as long as impregnation can becarried out. In addition, opposing contact rolls can be added in caseswhere the impregnation pressure is increased to enhance the degree ofimpregnation. Furthermore, as described in FIG. 4 in WO2015/076981, itis also possible to attempt to increase the production speed of prepregby arranging a conveyor belt opposite to “S-wrap rolls” and therebyenhancing impregnation efficiency. Alternatively, as described inWO2017/068159, JP2016-203397A, and the like, it is also possible toenhance impregnation efficiency by subjecting prepreg to ultrasonicationto heat the prepreg rapidly before impregnation. Alternatively, asdescribed in JP2017-154330A, it is also possible to use an impregnationdevice in which a plurality of “squeeze blades” are vibrated by anultrasonic generator. Alternatively, as described in JP2013-22868A, itis also possible to fold a prepreg up and carry out impregnation.

<Simplified Additional-Impregnation>

The above description shows an example in which a conventionaladditional-impregnation device is applied, but, in some cases, thetemperature of the primary impregnate prepreg is still high immediatelyafter the coating section, and in such cases, it is also possible tosimplify and make smaller an impregnation device significantly by addingan additional-impregnation operation at a stage where time has not yetelapsed very much after the prepreg exits from the coating section,thereby omitting or simplifying a heating device such as a hot plate forheating the primary impregnate prepreg again. An impregnation devicepositioned immediately after the coating section is referred to as asimplified additional-impregnation device. As a simplifiedadditional-impregnation device, heated nip rolls and heated S-shapedarranged rolls can be used. Compared with a usual impregnation device,they make it possible not only to decrease the roll diameter, the setpressure, and the contact length between the primary impregnate prepregand the rolls, thereby enabling the device to be smaller, but also todecrease the power consumption, and accordingly, are preferable.

In addition, applying a release sheet to the primary impregnate prepregbefore the primary impregnate prepreg enters the simplifiedadditional-impregnation device enhances the running properties of theprimary impregnate prepreg, and accordingly, is preferable.

FIG. 17 shows an example of a prepreg production process including asimplified additional-impregnation device. A simplifiedadditional-impregnation device 453 is arranged immediately after acoating section 430. Here, nip rolls are shown as an example of thesimplified additional-impregnation device 453, and the nip rollerpreferably includes a heating mechanism. In addition, the number ofstages of the nip rolls can be suitably selected depending on thepurpose, and is preferably three or less from the viewpoint of processsimplification (FIG. 17 shows an example of two stages). In addition,the nip roller preferably includes a driving device from the viewpointof easy tension control for conveyance of a prepreg. The nip pressurecan be suitably adjusted in accordance with a desired degree ofimpregnation.

In order that the primary impregnate prepreg cannot stick to the surfaceof the nip roll, it is preferable that the surface preliminarilyundergoes a suitable release treatment, or that a release sheet isinserted between the primary impregnate prepreg and the nip roll. Incases where a release sheet is inserted between the primary impregnateprepreg and the nip roll, it is also possible that the sheet is insertedfrom the coating section 430 side, and that the release sheet isdetached from the primary impregnate prepreg at the rolls on the hightension take-up device 444 side. The detached release sheet may bedirectly wound up, or may circuit so as to be inserted from the coatingsection 430 side again.

In addition, examples of additional-impregnation devices that can beused include not only nip rolls but also the above-mentioned “S-wraproll”, a fixing bar, and the like.

<Prepreg>

A prepreg mentioned in the present invention refers to a reinforcingfiber sheet having a matrix resin applied thereto, and is atwo-dimensional sheet-like intermediate base material to be used toproduce FRP. To the extent which does not depart from this meaning, whatis called a pultruded (pultrusion) material is also included in examplesof the prepreg in the present invention. As below-mentioned, the prepregis not limited to any particular width, and may be produced in the formof a tape having a narrow width or produced to have a broad width of upto approximately 2 m. In addition, the prepreg is not limited to anyparticular thickness, and generally has a thickness of approximately0.05 mm to 1 mm.

In a prepreg obtained by a production method according to the presentinvention, the impregnation ratio of a matrix resin is desirably 10% ormore. As to the state of impregnation with the matrix resin, a sampledprepreg can be torn off so that the inside of the prepreg can bevisually checked to see how the prepreg has been impregnated. Morequantitatively, the impregnation ratio can be evaluated, for example, bya peeling method. Measuring the impregnation ratio of the matrix resinby a peeling method can be carried out in the following manner. That is,a sampled prepreg is sandwiched between adhesive tapes, these are peeledoff, and the reinforcing fiber to which the matrix resin has stuck andthe reinforcing fiber to which the matrix resin has not stuck areseparated. Then, the ratio of the mass of the reinforcing fiber to whichthe matrix resin has adhered with respect to the mass of the wholereinforcing fiber sheet that has been used can be regarded as animpregnation ratio of the matrix resin based on a peeling method. Incases where the prepreg has a high degree of impregnation, the degree ofimpregnation can also be evaluated using a water absorption rate basedon the capillarity phenomena of the prepreg. Specifically, a methoddescribed in Japanese Translation of PCT International ApplicationPublication No. JP-T-2016-510077 can be used, wherein one side of aprepreg cut to 10 cm×10 cm is immersed by 5 mm in water for fiveminutes, causing a change in the mass, from which change theimpregnation ratio can be calculated.

<Prepreg Width>

The width of a prepreg is not limited to a particular one, and the widthmay be broad, tens of centimeters to approximately two meters, or may betape-like, several millimeters to tens of millimeters. The width can beselected in accordance with the application. In recent years, a devicecalled ATL (Automated Tape Laying) or AFP (Automated Fiber Placement) inwhich narrow prepregs or prepreg tapes are automatically laminated haswidely been used to make a prepreg laminating step more efficient, andthe width is also preferably adapted to such a device. ATL ofteninvolves use of narrow prepregs having a width of approximately 7.5 cm,approximately 15 cm, and approximately 30 cm, and AFP often involves useof prepreg tapes having a width of approximately 3 mm to approximately25 mm.

A method of obtaining a prepreg having a desired width is not limited toa particular one, and a method in which a broad prepreg having a widthof approximately 1 m to approximately 2 m is slit into narrow prepregscan be used. Alternatively, in order to simplify or omit the slittingstep, the width of the coating section used in the present invention canbe adjusted so as to be a desired width from the beginning. For example,in cases where a narrow prepreg having a width of 30 cm is produced forATL, the width of the outlet of the coating section can be adjusted inaccordance with the former width. Further in order to produce thisprepreg efficiently, it is preferable to produce a product having awidth of 30 cm, and juxtaposing a plurality of such productionapparatuses enables prepregs to be produced in a plurality of linesusing the same running devices, conveyance devices, various rolls, andwinders.

FIG. 18 shows an example in which five coating sections are linked inparallel. Here, five reinforcing fiber sheets 416 may pass through therespective independent five coating sections 430 to yield five primaryimpregnate prepregs 471, or the coating sections 430 may be integratedin parallel. In this case, the coating sections 430 have only to includefive independent width regulation mechanisms and five independentcoating section outlet widths.

In addition, prepreg tapes can be obtained by forming a reinforcingfiber sheet from approximately one yarn to four yarns of tape-likereinforcing fiber bundles and allowing the resulting reinforcing fibersheet to pass through the coating section the width of which is adjustedto afford a desired tape width. For prepreg tapes, particularly theaccuracy of the tape width is often required, from the viewpoint ofcontrolling cross-directional overlapping between the tapes. Because ofthis, it is preferable to control the coating section outlet width morestrictly, and in this case, it is preferable that the above-mentioned L,L2, and W satisfy the relationship(s) of L≤W+1 mm and/or L2≤W+1 mm.

<Slit>

The method of slitting prepreg is not limited to a particular one, and aknown slitting device can be used. A prepreg may be slit after theprepreg is once wound up and separately mounted in a slitting device,or, to obtain efficiency, a slitting step may be disposed continuouslyafter a prepreg production step without once winding up the prepreg. Inaddition, the slitting step may be a step in which a 1 m or more broadprepreg is directly slit into prepregs having a desired width, or oncecut and split into approximately 30 cm narrow prepregs and then slitagain into prepregs having a desired width.

Here, in cases where the above-mentioned plurality of coating sectionsfor narrow prepregs or prepreg tapes are juxtaposed, the respectiveindependent release sheets may be supplied, or a plurality of prepregsheets may be laminated on one broad release sheet that has beensupplied. The width direction edges of the prepreg thus obtained can becut off and supplied into an ATL or AFP device. In this case, the majorpart of the edges to be cut off is from the release sheet, andaccordingly, the amount of the matrix resin component (the resincomponent in the case of FRP) sticking to the slit cutter blade can bedecreased, resulting in being also advantageous in that the cleaningcycle for the slit cutter blade can be extended.

Variation and Application of the Present Invention

In the present invention, a plurality of coating sections can be used toattempt to make the production process more efficient and more highlycapable.

For example, a plurality of coating sections can be arranged so that aplurality of prepregs can be laminated. FIG. 19 shows an example of anaspect in which prepregs are laminated using two coating sections. Twoprimary impregnate prepregs 471 withdrawn from a first coating section431 and a second coating section 432 pass by a diverting roll 445, andlaminated at a lamination roll 447 downstream of the diverting roll.When this is done, positioning a release sheet between the primaryimpregnate prepreg 471 and the diverting roll can suppress the adhesionof the prepreg to the roll and stabilize the running, and thus, ispreferable. In this regard, the diverting roll can be replaced with adiverting guide provided with release treatment, or replaced with thelike.

Such a lamination type of prepreg makes it possible to attempt to makethe prepreg lamination step efficient, and is effective, for example, inproduction of a thick type of FRP. In addition, laying up prepregs of athin type into a multilayer laminate makes it possible to expect thatthe FRP toughness and the impact resistance are enhanced, and applyingthe present production method enables a thin type of multilayerlaminated prepreg to be obtained efficiently. Furthermore, laminatingdifferent kinds of prepregs easily enables a hetero-bound prepreg havingfunctionality imparted thereto to be obtained easily. In this case, itis possible to change the kind and fineness of the reinforcing fiber,the number of filaments, the mechanical property, the fiber surfaceproperty, and the like. In addition, the matrix resin (a resin in thecase of prepreg) used can also be a different one. For example, ahetero-bound prepreg in which different prepregs having differentthicknesses or different prepregs having different mechanical propertiesare laminated can be obtained. In addition, a prepreg that can achieveboth mechanical properties and tackiness properties can be obtainedeasily by applying a resin having excellent mechanical properties in thefirst coating section, applying a resin having excellent tackinessproperties in the second coating section, and laminating these.Conversely, a resin having no tackiness properties can also be disposedon the surface. It is also possible to apply a particle-free resin inthe first coating section and apply a particle-containing resin in thesecond coating section.

In another aspect, a plurality of coating sections can be juxtaposedwith respect to the running direction of the reinforcing fiber sheet,that is, a plurality of coating sections can be juxtaposed in the widthdirection of the reinforcing fiber sheet, as illustrated in FIG. 18 anddescribed above. This enables narrow or tape-like types of prepregs tobe produced efficiently. In addition, using different reinforcing fibersand different matrix resins for different coating sections makes itpossible to obtain a prepreg having properties varying in the widthdirection.

In another aspect, a plurality of coating sections can also be disposedin series in the running direction of the reinforcing fiber sheet. Sucha serial type of disposition enables the kinds of matrix resins to bevaried in the thickness direction of the primary impregnate prepreg. Inaddition, even using the same kind of matrix resin enables the runningstability and the high-speed running properties to be enhanced byallowing the coating conditions to vary depending on the coatingsection. For example, a prepreg that can achieve both mechanicalproperties and tackiness properties can be obtained easily by applying aresin having excellent mechanical properties in the first coatingsection, applying a resin having excellent tackiness properties in thesecond coating section, and laminating these. Conversely, a resin havingno tackiness properties can also be disposed on the surface. It is alsopossible to apply a particle-free resin in the first coating section andapply a particle-containing resin in the second coating section.

As above-mentioned, some aspects in which a plurality of coatingsections are disposed have been shown, the number of coating sections isnot limited to a particular one, and the aspects can be applied invarious manners in accordance with the purpose. Needless to say, thesetypes of dispositions can also be combined. Furthermore, the varioussizes, shapes, and coating conditions (temperature and the like) of thecoating section can be used in mixture.

As described above, the production method according to the presentinvention not only enables the production to be efficient and stable butalso enables the product to be made high-performance and capable, andhas excellent extendability.

<Matrix Resin Supply Mechanism>

In the present invention, the matrix resin is stored in the coatingsection, but it is preferable to replenish the matrix resin suitablybecause the coating progresses. The mechanism for supplying the coatingsection with a matrix resin is not limited to a particular one, and aknown device can be used. Supplying the coating section with a matrixresin continuously makes it possible not to disturb the liquid surfaceat the top of the coating section and to stabilize the running of thereinforcing fiber sheet, and accordingly, is preferable. For example,the matrix resin can be supplied by its own weight as a driving forcefrom a vessel storing the matrix resin, or supplied continuously using apump or the like. As a pump, a gear-pump, tube pump, pressure pump, andthe like can suitably be used in accordance with the properties of thematrix resin. In addition, in cases where the matrix resin is solid atroom temperature, a melter is preferably provided at the upper portionof the storage vessel. In addition, a continuous extruder and the likecan be used. As to the supply amount of the matrix resin, a mechanismfor enabling the matrix resin to be supplied continuously in accordancewith the coating amount is preferably provided so that the liquid levelof the matrix resin in the upper portion in the coating section can beas constant as possible. For this, for example, a mechanism in which theliquid level and the coating section weight are monitored and fed backto a supply device is conceivable, as above-mentioned.

<On-line Monitoring>

In addition, a mechanism for allowing the coating amount to be monitoredon-line is preferably provided in order to monitor the coating amount.The on-line monitoring method is not limited to a particular one, and aknown one can be used. For example, as a device for thicknessmeasurement, for example, a β-ray gauge can be used. In this case, thecoating amount can be estimated by measuring the thickness of areinforcing fiber sheet and the thickness of a prepreg and analyzing thedifference between the thicknesses. The coating amount monitored on-linecan immediately be fed back to the coating section, and utilized toadjust the temperature of the coating section and the gap D in thenarrowed section 23 (see FIG. 1). Needless to say, the coating amountmonitoring can be used as defect monitoring. As to the thicknessmeasurement position, for example, in FIG. 15, the thickness of thereinforcing fiber sheet 416 can be measured before the sheet isintroduced into the coating section 430, and the thickness of theprepreg can be measured between the coating section 430 and the hightension take-up device 444. In addition, on-line defect monitoring ispreferably carried out using infrared, near-infrared, camera (imageanalysis), and the like.

The coating device according to the present invention has a runningmechanism and a coating mechanism, wherein the running mechanism allowsa reinforcing fiber sheet, which is unidirectionally arrangedreinforcing fibers, to run vertically downward, and wherein the coatingmechanism is capable of storing the matrix resin in the inside thereof,and further includes a liquid pool and a narrowed section which are incommunication with each other, wherein the liquid pool has a portionwhose cross-sectional area decreases continuously along the runningdirection of the reinforcing fiber sheet, and wherein the narrowedsection has a slit-like cross-section and has a smaller cross-sectionalarea than the top side of the liquid pool.

Below, the present invention will be described in detail with referenceto a specific example in which a prepreg is produced using the coatingdevice. In this regard, the following description is an example, and thepresent invention is not construed to be limited to the aspect describedbelow.

FIG. 15 is a schematic diagram of an example of a process/device ofproducing a prepreg using the present invention. A plurality ofreinforcing fiber bobbins 412 are fit onto creels 411, and thereinforcing fibers pass by the diverting guides 413 and withdrawn. Here,a braking mechanism provided in the creel enables the reinforcing fiber414 to be withdrawn at a constant tension. A plurality of thereinforcing fibers 414 that have been withdrawn are orderly arranged bya reinforcing fiber arrangement device 415 to form a reinforcing fibersheet 416. Here, FIG. 15 depicts only three yarns of reinforcing fiber,but in reality, one yarn to hundreds of yarns are possible, andadjustments can be made to afford a desired prepreg width and fiberareal weight. Then, the reinforcing fiber sheet passes through a fiberbundle widening device 417 and a smoothing device 418, passes throughconveyance rolls 419, and is introduced into a reinforcing fiber sheetpreheating device 420 and the coating section 430. The reinforcing fibersheet preheating device 420 can be used to match the temperature of thematrix resin in the coating section to the temperature of thereinforcing fiber sheet as closely as possible, and can be omitted. InFIG. 15, the reinforcing fiber sheet 416 is linearly conveyed betweenthe devices from the reinforcing fiber arrangement device 415 to theconveyance rolls 419. In this regard, the fiber bundle widening device417 and the smoothing device 418 can be skipped suitably, or omitteddepending on the purpose. In addition, the arrangement order of thereinforcing fiber arrangement device 415, the fiber bundle wideningdevice 417, and smoothing device 418 can suitably be changed inaccordance with the purpose. The reinforcing fiber sheet 416 runsslantingly downward from the conveyance rolls 419, passes through thecoating section 430, and reaches the high tension take-up device 444.For the coating section 430, an arbitrary shape of the coating sectioncan be adopted to the extent that the object of the present inventioncan be achieved. Examples include such shapes as in FIG. 9 to FIG. 12,FIG. 14, FIG. 27, FIG. 29, and FIG. 32. In addition, a width regulationmechanism can be provided as in FIG. 8, if necessary. In FIG. 15,release sheets or resin films 446 unwound from supply devices 442 and443 can be laminated onto the primary impregnate prepreg 471 on the hightension take-up device 444. Here, the resin film or the release sheetmay be used singly, or a laminate of the resin film and the releasesheet may be used. In this case, the face of the resin film ispreferably adhered tightly to the surface of the prepreg. A releasepaper sheet, a release film, or the like can be used as a release sheet.FIG. 15 depicts nip rolls as the high tension take-up device 444. Then,the sheet-like integrated object passes through anadditional-impregnation device 450 including hot plates 451 and heatednip rolls 452, is cooled in a cooling device 461, is taken up by atake-up device 462, followed by peeling off the release sheet 446, andthen, is wound up in a winder 464, whereby a sheet-like integratedobject 472 composed of prepreg and a release sheet can be obtained as aproduct. The sheet-like integrated object is conveyed basically linearlyfrom the high tension take-up device 444 to the winder 464, andaccordingly, generation of wrinkles can be suppressed. Here, thedepiction of a matrix resin supply device and an on-line monitoringdevice is omitted in FIG. 15.

FIG. 16 is a schematic diagram of another example of a process/devicefor producing a prepreg using the present invention. FIG. 16 depicts anexample in which two sets of two heated S-shaped arranged rolls 455(four rolls in total) of an “S-wrap roll” type are used as anadditional-impregnation device, but the number of rolls may be larger orsmaller in accordance with the purpose. In addition, FIG. 16 depictscontact rolls 456 for enhancing the impregnation effect, but the contactrolls can be omitted depending on the purpose.

FIG. 17 is a schematic diagram of another example of a process/devicefor producing a prepreg using the present invention. Shown here is anexample in which a simplified additional-impregnation device is used. InFIG. 17, a simplified additional-impregnation device 453 is installedimmediately after the coating section 430, and accordingly, the prepreg471 in a high-temperature state is introduced into the simplifiedadditional-impregnation device 453, so that the impregnation device canbe simplified and made smaller. In FIG. 17, heated nip rolls 454 aredepicted as an example, but needless to say, smaller heated S-shapedarranged rolls may be used depending on the purpose. Use of a simplifiedadditional-impregnation device also has an advantage in that the wholeprepreg production device can be made very compact. In particular, incases where the resin film 446 is a particle-containing resin film,increasing the degree of impregnation of the primary impregnate prepregmakes it possible to allow the particles in the resin film to bearranged in the surface layer of the prepreg in the subsequent step, andthus, is preferable.

Below, an embodiment of the present invention will be described withreference to an example in which the effect of the portion whosecross-sectional area decreases intermittently in the liquid pool wasverified by simulation.

In carrying out the simulation, a software STAR-CCM+ manufactured bySiemens AG was used, and the Navier-Stokes equation was solved fornumerical analysis of the liquid flow and liquid pressure in the portionwhose cross-sectional area decreases intermittently. More specifically,the portion whose cross-sectional area decreases intermittently wasmodeled as a fluid portion, and the premise was made that the fluidportion is a two-dimensional flow, i.e., that the fluid (matrix resin)flows only on the X-Z plane and does not flow in the direction Y. Inthis case, the viscosity of the fluid was 10 Pa·s, the density was 1000kg/m³, and the running speed of the reinforcing fiber sheet was set to20 m/minute. The analysis results obtained with θ=30° and H=50 mm areshown in FIG. 20 and FIG. 21. In this regard, the analysis was premisedwith a plane symmetry with respect to the reinforcing fiber sheet, andthus, only the upper half is shown in the drawings.

As shown in FIG. 20, it is revealed that the liquid pressure increasesin the direction toward the outlet of the portion whose cross-sectionalarea decreases intermittently in the liquid pool, and that the largestliquid pressure is 0.782 MPa, which is high. In addition, as shown inFIG. 21, it is revealed that the accompanying flow on the reinforcingfiber sheet is turned back at the high-pressure liquid portion to form acircular stream. In addition, FIGS. 22 and 23 show an example in whichthe taper length (i.e., H) was 1 mm, and the calculation result revealedthat the largest liquid pressure was 0.640 MPa, which was lower thanwith H=50 mm, but that the liquid pressure was still high (FIG. 22).FIG. 23 shows the state where, in this way, a flow in the directionopposite to the running direction of the reinforcing fiber sheet wasformed in the vicinity of the narrowed section.

On the other hand, FIGS. 24 and 25 show the calculation result obtainedfrom a case in which H=0 mm, i.e. the liquid pool had no portion whosecross-sectional area decreases intermittently. This has revealed thecalculation result that the largest liquid pressure was 0.166 MPa, whichwas quite lower (approximately 1/4) than with H=1 mm. In combinationwith the facts that the liquid pressure was low and that no taperedportion was in the vicinity of the narrowed section, the results suggestthat the flow in the direction along the outlet side member was large inthe vicinity of the narrowed section, and that the formation of a flowin the direction opposite to the running direction of the reinforcingfiber sheet was weak (FIG. 25).

In comparison, FIG. 26 shows that the flow velocity with H changed wasshaded according to the grayscale in order to consider, in detail, theformation of a circular stream with respect to the taper length H. Thediagram of the flow velocity shows that a darker shade means a higherflow velocity. First, referring to the diagrams showing the flowdirection of the liquid, a circular stream appears to have been formedwith H=0, but referring to the diagrams of the flow velocity, it isunderstood that, with H=0 mm, the liquid flowed once away from thenarrowed section, and then, flowed in the direction opposite to therunning direction of the reinforcing fiber sheet, and that the flowvelocity is lower (more lightly shaded in the diagram) than with H=1 mm.This derives the thought that the formation of a circular stream isquite weak with H=0 mm, making it impossible to obtain the effects ofthe present invention. Next, with H=50 mm, the flow velocity of the flowin the direction opposite to the running direction of the reinforcingfiber sheet is larger (more shaded) than with H=1 mm obviously in thevicinity of the narrowed section and also apart therefrom, showing thatthe formation of a circular stream is strong, allowing the effects ofthe present invention to be highly achieved. Furthermore, with H=0 mmand H=1 mm, the liquid flow is extremely smaller toward the corner inthe direction away from the narrowed section (the upper right corner inthe drawing), revealing that a stagnant portion is formed. Such astagnant portion, if any, makes it more likely to deteriorate the matrixresin, which is liquid. This portion is cured particularly in caseswhere a thermosetting resin is used as the matrix resin. The curedobject is carried in the liquid, and in some cases, acts as foreignmatter which disturbs the processes and decreases the quality of theresulting prepreg. It is understood, however, that such a stagnantliquid portion is more unlikely to be generated in cases where theportion whose cross-sectional area decreases intermittently is long aswith H=50 mm, which is thus advantageous for the process stabilizationand the enhancement of the quality of the prepreg.

The above-mentioned has shown the effect of having a portion whosecross-sectional area decreases intermittently and the fact that a largervalue of H causes a higher liquid pressure as well as a larger circularstream, and has revealed that a larger value of H enables the effect ofthe present invention to be higher.

Below, illustrations in which a prepreg is obtained by a method ofproducing a prepreg according to the present invention will bedescribed. However, the present invention is not construed to be limitedto such illustrations.

<Illustration 1: Thermosetting Broad Prepreg (1)>

The coating section type 20f in the form depicted in FIG. 27 can be usedas a coating section, and an apparatus obtained by removing a fiberbundle widening device, a smoothing device, and anadditional-impregnation device from an apparatus configured as describedin FIG. 15 (the depiction of a resin supply section is omitted) can beused as a prepreg production apparatus.

The side wall member of the coating section is formed from an acrylicresin plate so that the state of the inside can be observed. Inaddition, the running direction of the reinforcing fiber sheet in theliquid pool is the horizontal direction, the liquid pool is tapered intwo tiers. The opening angle of the first-tier taper can be 15 to 20°,and the taper can have a length (i.e., H) of 10 to 70 mm, and theopening angle of the second-tier taper can be 5 to 10°. In addition, aplate-like bush conformed to the internal shape of the coating sectionis provided as a width regulation mechanism, as described in FIG. 8, andfurthermore, the installation position of the plate-like bush is madefreely variable so that L2 can suitably be adjusted. The width U of thenarrowed section can be adapted to become 300 mm in cases where L2 is300 mm. The gap D in the narrowed section is approximately 0.18 mm, andcan be adjusted in accordance with a desired areal weight. In this case,the aspect ratio of the outlet slit was 1500. In addition, the spaceexternal to each bush can be closed off at the outlet side of thenarrowed section so that the matrix resin cannot leak through the outletof the narrowed section. In addition, the distance B defined by theupper side of the liquid pool and the upper side of the storage portioncan be 50 to 70 mm. In addition, the length C of the liquid pool can beshortened in a range which enables the reinforcing fiber sheet to run,and specifically, the length can be 100 to 200 mm.

Carbon fiber (“TORAYCA®” T800S (24K), manufactured by Toray Industries,Inc.) or the like can be used as a reinforcing fiber, and thebelow-mentioned thermosetting epoxy resin composition can be used as amatrix resin. In addition, the number of reinforcing fiber bobbins canbe changed in accordance with the areal weight of a prepreg to beproduced, and using 56 yarns makes it possible to obtain a prepreghaving a common areal weight.

A prepreg can be produced using a bisphenol type epoxy resin (“jER®”825, manufactured by Mitsubishi Chemical Corporation) as a matrix resinat room temperature (with the resin viscosity corresponding to 4 to 7Pa·s) with the running speed of the reinforcing fiber sheet and theprepreg set to 5 to 25 m/minute.

As in the present illustration, using a coating section made of atransparent material such as acryl enables the inside of the coatingsection to be observed, thus making it possible to evaluate the runningproperties of the reinforcing fiber sheet. More specifically, thecontinuous running properties can be evaluated as below-mentioned. Thatis, the reinforcing fiber sheet is run continuously for 30 minutes. Onewhich causes no fuzz clogging nor yarn breaking is rated as “Good”, andone which causes fuzz clogging and yarn breaking is rated as “Bad”. Inaddition, to evaluate a sign of fuzz clogging, the coating section isdismantled after each of the 60-minute and the 120-minute continuousrunning, the liquid contact surface of the upper-side member is checkedby visual observation for fuzz. The fuzz prevention properties by virtueof which fuzz stuck to or to the vicinity of the narrowed section afterthe continuous running are rated as “Poor”; the fuzz preventionproperties by virtue of which fuzz stuck to the portion far from thenarrowed section (on or near the boundary between the portion whosecross-sectional area does not decrease and the portion whosecross-sectional area decreases continuously) after the continuousrunning are rated as “Fair”; the fuzz prevention properties by virtue ofwhich no fuzz stuck to the liquid contact surface of the upper-sidemember after the continuous running are rated “Good”. In addition, thereinforcing fiber sheet is run continuously at a running speed of 20m/minute for 60 minutes, and a measurement is made of the time duringwhich the reinforcing fiber sheet is run uniformly without having anysplit of the reinforcing fiber bundle (parts at which the sheet-likereinforcing fiber bundle is torn in streaks) or any edge folding of thereinforcing fiber bundle (parts at which the reinforcing fiber bundle isfolded over) on the boundary between the portion whose cross-sectionalarea does not decrease and the portion whose cross-sectional areadecreases continuously. The reinforcing fiber sheet that is rununiformly without any split of the fiber bundle or any edge folding ofthe fiber bundle during the time the ratio of which is 90% or more ofthe whole running time is rated as “Excellent”, 50% or more and lessthan 90% “Good”, 10% or more and less than 50% “Fair”, less than 10%“Poor”.

In the present illustration, setting the running speed of thereinforcing fiber sheet to approximately 20 m/minute, which is a highspeed, still makes it possible that fuzz/yarn clogging does not occur(Good) with H≥30 mm, and also that the fuzz prevention properties areGood. In addition, setting the relationship L2−W between the width L2 ofthe lower end of the width regulation mechanism and the width W of theprimary impregnate prepreg to 0≤L2−W≤W+2 (mm) makes it possible that thesplitting of the reinforcing fiber bundle is Excellent, and that theedge folding of the reinforcing fiber bundle is Excellent.

In addition, suitably adjusting the taper shape and the gap D in thenarrowed section makes it possible that the impregnation ratio based ona peeling method is 50% or more. The impregnation ratio based on apeeling method can be calculated from the ratio of the mass of thereinforcing fiber to which a matrix resin has stuck with respect to themass of the whole reinforcing fiber sheet that has been used, in which asampled prepreg is sandwiched between adhesive tapes, these are peeledoff, and the reinforcing fiber to which the matrix resin has stuck andthe reinforcing fiber to which the matrix resin has not stuck areseparated.

In addition, the areal weight of a 100 mm square in the width directionof the thus obtained primary impregnate prepreg can be brought withinthe range of ±2 mass % for both a carbon fiber and a resin, making itpossible to obtain an excellent areal weight uniformity in the widthdirection. In this regard, the uniformity of the areal weight of theprepreg in the width direction can be evaluated as below-mentioned. A300 mm wide prepreg is cut into a right edge, a center portion, and aleft edge in the width direction, 100 mm square each, and the mass ofthe prepreg and the mass of the carbon fiber are each measured with n=3.The mass of the carbon fiber is measured as a residue obtained byeluting the resin from the prepreg with a solvent. From these, theaverage values for the sampling positions are calculated, and theaverage values for the sampling position are compared.

<Illustration 2: Thermosetting Broad Prepreg (2)>

The coating section can be made of stainless steel. Furthermore, to heatthe matrix resin, a plate-heater can be attached to the periphery of thecoating section, and the temperature and viscosity of the matrix resincan be adjusted while the temperature is measured with a thermocouple.In other respects, the same coating section, prepreg productionapparatus, and reinforcing fiber sheet as in the above-mentionedillustration 1 can be used.

Next, a matrix resin A that is a thermosetting epoxy resin compositioncan be used as a matrix resin. This is a mixture of an epoxy resin (amixture of an aromatic amine type of epoxy resin and a bisphenol type ofepoxy resin), a hardener (diaminodiphenyl sulfone), andpolyethersulfone, and contains no polymer particles. The viscosity ofthis matrix resin A can be measured using the ARES-G2 manufactured by TAInstruments, Inc., and is 50 Pa·s at 75° C., 15 Pa·s at 90° C., and 4Pa·s at 105° C., at a measurement frequency of 0.5 Hz at a temperatureramp rate of 1.5° C./minute. Using this matrix resin A, a prepreg can beproduced with the matrix resin temperature set to 75 to 105° C. in thecoating section and with the running speed of the reinforcing fibersheet and the prepreg set to 5 to 25 m/minute.

For example, a prepreg can be produced with a coating section having afirst-tier taper at an opening angle of 17° and a second-tier taper atan opening angle of 7°, with H=70 mm and L2−W=0 mm, with the matrixresin temperature set to 90° C. in the coating section, and with therunning speed of the reinforcing fiber sheet and the prepreg set to 20m/minute. Evaluating the high-speed running properties of the resultingprepreg can bring the results that no fuzz/yarn clogging occurs and thatthe fuzz prevention properties are Good. In addition, it is madepossible that the degree of impregnation based on a peeling method is50% or more, and that the areal weight uniformity in the width directionis brought within the range of ±2%.

<Illustration 3: Thermosetting Broad Prepreg (3)>

In this illustration, a simplified additional-impregnation process and aresin film lamination process carried out thereafter will be described.The coating section can be the same as in the illustration 2, and theprepreg production apparatus that can be used is the same as depicted inFIG. 28.

A primary impregnate prepreg can be obtained by coating the reinforcingfiber sheet mentioned in the illustration 2 with the matrix resin A alsomentioned in the illustration 2 at 80 to 100° C. Then, anadditional-impregnation process is carried out in anadditional-impregnation device installed immediately after the coatingsection, thus enabling the degree of impregnation to be increased sothat the impregnation ratio based on a water absorption rate can be 3 to15%. When this is done, the simplified additional-impregnation devicecan be a multi-stage nip roll, and in addition, a release sheet can beinserted on the nip roll. In addition, this release sheet is allowed tocircuit. The impregnation ratio based on a water absorption rate can becalculated from a change in a mass in accordance with a method describedin Japanese Translation of PCT International Application Publication No.JP-T-2016-510077, wherein one side of a prepreg cut to 10 cm×10 cm isimmersed by 5 mm in water for five minutes, causing the change in themass. Then, a resin film(s) is/are laminated on one face or both facesof the prepreg having a high degree of impregnation, and this resultingprepreg is introduced into an additional-impregnation machine, in whichthe impregnation ratio can be adjusted to 0.1 to 15%. The running speedof the reinforcing fiber sheet and the prepreg can be 5 to 25 m/minute.

For example, a prepreg can be produced with a coating section having afirst-tier taper at an opening angle of 17° and a second-tier taper atan opening angle of 7°, with H=70 mm and L2−W=0 mm, with the matrixresin A temperature set to 90° C. in the coating section, with thesurface temperature of the nip roll in the simplifiedadditional-impregnation device set to 100° C., with use of a resin filmwhich is a laminate of the below-mentioned matrix resin B film and arelease sheet, and with the running speed of the reinforcing fiber sheetand the prepreg set to 20 m/minute. The prepreg enables the impregnationratio based on a water absorption rate to be approximately 5%. Here, thematrix resin B is a thermosetting epoxy resin composition, which isobtained by adding “particle 3” (having a Tg of 150° C.) described inEXAMPLES in JP2011-162619A as polymer particles to a mixture of an epoxyresin (a mixture of an aromatic amine type of epoxy resin and abisphenol type of epoxy resin), a hardener (diaminodiphenyl sulfone),and polyethersulfone, such that the polymer particles account for 13mass % of the whole mass of the resin composition as 100 mass %. Theviscosity of this resin is 118 Pa·s at 75° C., 32 Pa·s at 90° C., and 10Pa·s at 105° C. as measured at a measurement frequency of 0.5 Hz at atemperature ramp rate of 1.5° C./minute. This matrix resin B formed intoa resin film by a known method can be used.

Such polymer particle-containing prepregs are laminated in six layers,and cured using an autoclave at 180° C. at 6 kgf/cm² (0.588 MPa) for twohours so that a CFRP can be obtained. The CFRP is enabled to have atensile strength of approximately 3.0 GPa, and can be said to havesuitable mechanical properties as a structural material for theaerospace. In this regard, the tensile strength of a CFRP is measured inthe same manner as in WO2011/118106, and the value resulting fromnormalizing the volume % of the reinforcing fibers in the prepreg to56.5% can be used. In addition, the cross-section of the resulting CFRPexhibits reinforcing fiber layers orderly laminated in the horizontaldirection and a matrix resin layer formed between a reinforcing fiberlayer and a reinforcing fiber layer, and furthermore, most of thepolymer particles can be arranged between these reinforcing fiberlayers. This state can be verified by observing the cross-section of theCFRP with an electron microscope or the like.

In this regard, a prepreg is produced by a conventional hot-melt processusing the carbon fiber and the matrix resin A, and the resulting prepregis cured using an autoclave at 180° C. at 6 kgf/cm² (0.588 MPa) for twohours to yield a CFRP, which is found to have a tensile strength ofapproximately 2.9 GPa.

<Illustration 4: Thermoplastic Prepreg Tape (1)>

Using the coating section 20 g depicted in FIG. 29 makes it possiblethat a plurality of reinforcing fiber sheets are allowed to pass througha plurality of diverting members included in the liquid pool, thusundergo an initial impregnation process, and are laminated andintegrated, furthermore that the matrix resin to be applied in thenarrowed section is used for measurement and impregnation, and also thatthe cross-section of the prepreg is shaped. In cases where a matrixresin composed mainly of a thermoplastic resin is used, particularly incases where super engineering plastics having high heat resistance areused, a high-temperature process in particular is required in theimpregnation process. Because of this, carrying out the impregnationprocess sufficiently in the coating section is effective in order todecrease the load in the additional-impregnation process. Suitableexamples thereof include a coating section depicted in FIG. 29. Inaddition, the inside of the coating section is preferably filled withinert gas such as nitrogen or argon in order to inhibit thermaldegradation and oxidative decomposition. For this purpose, a sealingmember is preferably provided at the opening to the extent that thereinforcing fiber sheet has no problem with running.

To produce a thermoplastic prepreg tape, the coating section 20 gdepicted in FIG. 29 has a first-tier taper at an opening angle of 15 to20° and a second-tier taper at an opening angle of 5 to 10°; H=50 to 70mm, L2−W=0 to 1 mm, B=30 to 70 mm, and C=250 to 350 mm are satisfied;the coating section is filled with nitrogen; and a degassing mechanismcan also be used. In addition, an apparatus depicted in FIG. 23 can beused as a prepreg production apparatus. The depiction of FIG. 30 showsthat three yarns of reinforcing fiber are arranged to form onereinforcing fiber sheet, and that two such sheets are used to produce aprepreg, but obviously, the number of reinforcing fiber bobbins and thatof reinforcing fiber sheets can be changed suitably. For example, carbonfiber (“TORAYCA®” T800S (24K), manufactured by Toray Industries, Inc.)is used as reinforcing fiber, three yarns of the fiber are used to formone reinforcing fiber sheet, and two such sheets are used to produce aprepreg having a width of 20 mm. In addition, a prepreg is produced witha low-viscosity polyamide 6 used as a matrix resin, and with thetemperature of the matrix resin in the coating section set to 280 to300° C. When this is done, the impregnation process can be completelycarried out with nip rolls for simplified additional-impregnationarranged immediately after the coating section as depicted in FIG. 30and with the surface temperature of the nip roll set to 200 to 250° C.The running speed of the reinforcing fiber sheet and the prepreg can be5 to 20 m/minute. A molded thermoplastic prepreg thus obtained has novoid therein, and can achieve good mechanical characteristics. In theapparatus depicted in FIG. 30, a calender roll and a pulling device canbe arranged downstream of the simplified additional-impregnation device,as described, for example, in Patent Literature 3.

<Illustration 5: Thermoplastic Prepreg Tape (2)>

In the above-mentioned illustration 4, the matrix resin can be changedto super engineering plastics. For example, in cases where PEEK is used,the impregnation process can be completely carried out with thetemperature of the matrix resin in the coating section set to 350 to420° C. and with the surface temperature of the nip roll for simplifiedadditional-impregnation set to 300 to 400° C. In addition, in caseswhere PEKK is used, the impregnation process can be completely carriedout with the temperature of the matrix resin in the coating section setto 380 to 420° C. and with the surface temperature of the nip roll forsimplified additional-impregnation set to 320 to 420° C. In addition,the running speed of the reinforcing fiber sheet and the prepreg can be5 to 20 m/minute. A molded thermoplastic prepreg thus obtained has novoid therein, and can achieve good mechanical characteristics and heatresistance.

EXAMPLES

<Prepreg Production Apparatus>

An apparatus configured as described in FIG. 31 (the depiction of aresin supply section is omitted) was used as a prepreg productionapparatus.

<Coating Section>

A coating section of the type of the coating section 20 h having theform depicted in FIG. 32 was used as a coating section, and the sideface members of the coating section were produced from an acrylic resinplate so that the state of the inside could be observed. However, onlythe narrowed section was made of stainless steel. In addition, therunning direction of the reinforcing fiber sheet was horizontal (0°) inthe portion whose cross-sectional area decreased along the runningdirection of the reinforcing fiber sheet in the liquid pool. The liquidpool was tapered in two tiers, the opening angle of the first-tier taperwas 17°, and the opening angle of the second-tier taper was 7°. Inaddition, plate-like bushes conformed to the internal shape of thecoating section were provided as a width regulation mechanism, asdescribed in FIG. 8, and L2 was 20 mm. The gap D in the narrowed sectionwas 0.18 mm. In addition, the space external to each bush was closed offat the outlet face of the narrowed section so that the matrix resincould not leak through the outlet of the narrowed section. In addition,the distance B between the lower face of the upper-side member and theupper face of the storage portion was 30 mm, wherein the member and thestorage portion were constituents of the coating section. In addition,the horizontal length C of the liquid pool was 120 mm. In addition, adiverting member for adjusting the running direction of the reinforcingfiber sheet in the coating section was disposed upstream of the portionwhose cross-sectional area decreased continuously in the liquid pool.

<Reinforcing Fiber Sheet>

A prepreg was produced using three yarns of carbon fiber (“TORAYCA®”T800S (24K), manufactured by Toray Industries, Inc.) as reinforcingfibers.

<Matrix Resin>

A bisphenol type epoxy resin (“jER®” 825, manufactured by MitsubishiChemical Corporation) was used as a matrix resin. The resin viscosity atroom temperature was 4 to 7 Pa·s (values in the catalog).

<Prepreg Production Process>

Reinforcing fibers were withdrawn from reinforcing fiber bobbins fitonto creels, three reinforcing fiber yarns were arranged in the widthdirection by a reinforcing fiber arrangement device to form areinforcing fiber sheet, and the resulting reinforcing fiber sheet wasintroduced into a coating section, so that the matrix resin was appliedto the sheet. Then, a prepreg was withdrawn from the coating section,release sheets were applied to the prepreg from above and below, and theresulting prepreg was wound up. In addition, the running speed of thereinforcing fiber sheet and the prepreg were 20 m/minute.

<Evaluation of Continuous Running Properties>

To evaluate the continuous running properties of a reinforcing fibersheet in the coating section, the reinforcing fiber sheet was runcontinuously for 30 minutes. One which caused no fuzz clogging nor yarnbreaking was rated as “Good”, and one which caused fuzz clogging andyarn breaking was rated as “Bad”.

In addition, to evaluate a sign of fuzz clogging, the coating sectionwas dismantled after each of the 60-minute and the 120-minute continuousrunning, the liquid contact surface of each of the wall constituentmembers was checked by visual observation for fuzz. The fuzz preventionproperties were evaluated as follows: the fuzz prevention properties byvirtue of which fuzz stuck to or to the vicinity of the narrowed sectionafter the continuous running were rated as “Poor”; the fuzz preventionproperties by virtue of which fuzz stuck to the portion far from thenarrowed section 23 (on or near the boundary between the portion whosecross-sectional area does not decrease and the portion whosecross-sectional area decreases continuously) after the continuousrunning were rated as “Fair”; the fuzz prevention properties by virtueof which no fuzz stuck to the liquid contact surface of the upper-sidemember after the continuous running were rated “Good”.

In addition, the reinforcing fiber sheet was run continuously at arunning speed of 20 m/minute for 60 minutes, and a measurement was madeof the time during which the reinforcing fiber sheet was run uniformlywithout having any split of the fiber bundle (parts at which thesheet-like carbon fiber bundle was torn in streaks) or any edge foldingof the fiber bundle (parts at which the carbon fiber bundle was foldedover) immediately above the liquid pool. The reinforcing fiber sheetthat was run uniformly without any split of the fiber bundle or any edgefolding of the fiber bundle during the time the ratio of which was 90%or more of the whole running time was rated as “Excellent”, 50% or moreand less than 90% “Good”, 10% or more and less than 50% “Fair”, lessthan 10% “Poor”.

<Evaluation of Degree of Impregnation (Peeling Method)>

A sampled prepreg was sandwiched between adhesive tapes, these werepeeled off, and the reinforcing fiber to which the matrix resin stuckand the reinforcing fiber to which the matrix resin did not stick wereseparated. Then, the ratio of the mass of the reinforcing fiber to whichthe matrix resin stuck with respect to the mass of the whole reinforcingfiber sheet that was used was determined by a peeling method, andregarded as an impregnation ratio of the matrix resin.

Examples 1 to 3

A prepreg was produced with the taper length (i.e., H) and the value ofL2−W changed as in Table 1. This has revealed that the larger the valueof H, the better the fuzz prevention properties, and that the smallerthe value of L2−W, the more unlikely it is that splitting and edgefolding of the reinforcing fiber sheet are caused.

In addition, the impregnation ratio based on a peeling method was 50 to60% in any of the Examples, revealing that the impregnation process waswell carried out in the coating section.

Comparative Example 1

A prepreg was produced with 12 mm as the value of L2−W as described inTable 1, with the result that splitting and edge folding of thereinforcing fiber sheet were caused.

Comparative Example 2

Using a coating section having no portion whose cross-sectional areadecreased continuously (H=0), an attempt was made to produce a prepregunder the conditions listed in Table 1 and in the same manner as inExample 1, but the reinforcing fiber sheet stuck immediately afterstarting to run at 20 m/minute, showing poor continuous runningproperties.

TABLE 1 Example Example Example Comparative Comparative 1 2 3 Example 1Example 2 Performing L2-W (mm) 0 0 0 12 0 Conditions Length H alongwhich 50 25 8 50 0 Cross-sectional Area Decreases Continuously (mm)Evaluation Continuous Running Good Good Good Good Bad Items PropertiesFuzz Prevention Good Good Fair Good — Properties (60 minutes) FuzzPrevention Good Fair Fair Fair — Properties (120 minutes) Split ofReinforcing Excellent Excellent Excellent Fair — fiber sheet EdgeFolding of Excellent Excellent Excellent Fair — Reinforcing fiber sheet

Example 4

Reinforcing fibers were withdrawn from reinforcing fiber bobbins fitonto creels, and three reinforcing fiber yarns were arranged in thethickness direction by the reinforcing fiber arrangement device toproduce a prepreg in the same manner as in Example 1 (L2−W=0). Here, L2was 7 mm. In addition, the gap D in the narrowed section was 0.5 mm. Theresults of evaluation of the running properties were Good for all of thecontinuous running properties and the fuzz prevention properties (for 60minutes and 120 minutes), and both of splitting and edge folding of thereinforcing fiber sheet were Excellent.

INDUSTRIAL APPLICABILITY

The prepreg obtained by the production method according to the presentinvention can widely be applied as FRP typified by CFRP, in aerospaceapplications, applications for structural materials and interiormaterials such as for automobiles, trains, and ships, pressure vessels,industrial material applications, sports material applications, medicalequipment applications, housing applications, civil engineering andconstruction applications, and the like.

REFERENCE SIGNS LIST

-   -   1 a Reinforcing fiber    -   1 b Reinforcing fiber sheet    -   1 c Primary Impregnate Prepreg    -   1 d Prepreg    -   2 Matrix Resin    -   3 Release Sheet    -   4 Resin Film    -   11 Creel    -   12 Reinforcing fiber Bobbin    -   13 Arrangement Device    -   14, 15 Conveyance Roll    -   16 a, 16 b Supply Device    -   17 Winder    -   20 Coating Section    -   21, 21 a, 21 b Wall Constituent Members    -   22 Liquid Pool    -   22 a Portion whose cross-sectional area does not decrease in        Liquid Pool    -   22 b Portion whose cross-sectional area decreases continuously        in Liquid Pool    -   22 c Portion whose cross-sectional area decreases intermittently        in Liquid Pool    -   23 Narrowed Section    -   24 Upper-side member    -   25 Lower-side member    -   26 Degassing Mechanism    -   27 Side Face Member    -   28 Outlet    -   29 Outlet Side Member    -   30 Opening    -   31 Diverting Member    -   32 Side Wall Member    -   33 Gap between Reinforcing fiber sheet 1 b and Side Wall Member        32    -   34, 34 a, 34 b Width Regulation Mechanism    -   40 Coating Section in Embodiment other than of Present Invention    -   41 Liquid Pool    -   42 Boundary    -   43 Storage Portion    -   44 Liquid Surface    -   45 Sealing Member    -   100 Coating Device    -   B Distance Defined by Upper Side of Liquid Pool 22 and Upper        Side of Storage Portion 43    -   C Length of Liquid Pool    -   D Gap    -   G Position at which width regulation is carried out    -   H Length of Portion 22 b whose cross-sectional area decreases        continuously in Liquid Pool    -   L Width of Liquid Pool 22    -   R, Ra, Rb Circular Stream in the Edge    -   T Circular Streams    -   U Width of Narrowed Section 23    -   W Width of Primary Impregnate Prepreg 1 c, as measured        immediately under Narrowed Section 23    -   X Running Direction of Reinforcing fiber sheet    -   Y Direction perpendicular to X and Z    -   Z Vertically Downward Direction    -   Opening Angle of Tapered Portion    -   411 Creel    -   412 Reinforcing fiber Bobbin    -   413 Diverting Guide    -   414 Reinforcing fiber    -   415 Reinforcing fiber Arrangement Device    -   416 Reinforcing fiber sheet    -   417 Fiber Bundle Widening Device    -   418 Smoothing Device    -   419 Conveyance Roll    -   420 Reinforcing fiber sheet Preheating Device    -   430 Coating Section    -   431 First Coating Section    -   432 Second Coating Section    -   442 Supply Device (Upper)    -   443 Supply Device (Lower)    -   444 High Tension Take-up Device    -   445 Diverting Roll    -   446 Resin Film or Release Sheet    -   447 Lamination Roll    -   450 Additional-impregnation Device    -   451 Hot Plate    -   452 Heated Nip Roll    -   453 Simplified Additional-impregnation Device    -   454 Heated Nip Roll    -   455 Heated S-shaped Arranged Roll    -   456 Contact Roll    -   461 Cooling Device    -   462 Take-up Device    -   463 Release Sheet (Upper) Wind-up Device    -   464 Winder    -   471 Primary Impregnate Prepreg    -   472 Prepreg/Release Sheet (Sheet-like Integrated Object)

1. A method of producing a prepreg, comprising a step of allowing areinforcing fiber sheet to pass horizontally or slantingly through theinside of a coating section storing a matrix resin to apply said matrixresin to said reinforcing fiber sheet; wherein said coating sectionincludes a liquid pool and a narrowed section which are in communicationwith each other, wherein said liquid pool has a portion whosecross-sectional area decreases continuously along a running direction ofsaid reinforcing fiber sheet, and wherein said narrowed section has aslit-like cross-section and has a smaller cross-sectional area than thelargest cross-sectional area of said liquid pool; and wherein the widthL at the ends of said liquid pool and the width W of said sheet-likereinforcing fiber bundle at the outlet of said narrowed section satisfythe relationship of the below-mentioned Formula (1):L≤W+10 (mm)  (1).
 2. The method of producing a prepreg according toclaim 1, wherein the running direction length of said portion whosecross-sectional area decreases continuously in said liquid pool is 10 mmor more.
 3. The method of producing a prepreg according to claim 1,wherein the width of said reinforcing fiber sheet is regulated in saidliquid pool.
 4. The method of producing a prepreg according to claim 1,comprising carrying out an additional-impregnation process on a primaryimpregnate prepreg withdrawn from said coating section.
 5. The method ofproducing a prepreg according to claim 1, comprising applying a resinfilm to at least one face of said primary impregnate prepreg withdrawnfrom said coating section.
 6. The method of producing a prepregaccording to claim 4, comprising applying a resin film to at least oneface of the prepreg formed after carrying out saidadditional-impregnation process.
 7. A coating device for applying amatrix resin to a reinforcing fiber sheet, comprising: a runningmechanism which allows the reinforcing fiber sheet to run horizontallyor slantingly, and a coating section; wherein said coating section iscapable of storing a matrix resin in the inside thereof, and furtherincludes a liquid pool and a narrowed section which are in communicationwith each other, wherein said liquid pool has a portion whosecross-sectional area decreases continuously along a running direction ofsaid reinforcing fiber sheet, and wherein said narrowed section has aslit-like cross-section and has a smaller cross-sectional area than thelargest cross-sectional area of said liquid pool.
 8. The coating deviceaccording to claim 7, wherein the upper portion of said coating sectionhas an opening through which said reinforcing fiber sheet is allowed topass.
 9. A prepreg production apparatus comprising: a rack on which areinforcing fiber or a reinforcing fiber fabric is hung; said coatingdevice according to claim 7; and a winder for winding up a prepreg.